Insect Bites 

Updated: Jun 21, 2018
Author: Boyd (Bo) D Burns, DO, FACEP, FAAEM; Chief Editor: Joe Alcock, MD, MS 

Overview

Background

Insects are arthropods of the class Insecta. Insects have an adult stage characterized by a hard exoskeleton, 3 pairs of jointed legs, and a body segmented into head, thorax, and abdomen. Insects comprise the most diverse and numerous class of the animal kingdom and include numerous species of praying mantis, dragonflies, grasshoppers, true bugs, flies, fleas, bees, wasps, ants, lice, butterflies, moths, and beetles. The number of species is estimated at between 6 and 10 million, with more than a million species already described. Insects represent more than half of all known living organisms and potentially represent more than 90% of the differing life forms on Earth. Hence, human contact with insects is unavoidable. Exposure to biting or stinging insects or to their remains can range in severity from benign or barely noticeable to life threatening.

See the image below.

Insect Bites. Louse, Pediculus humanus, dorsal vie Insect Bites. Louse, Pediculus humanus, dorsal view after feeding on blood. Most lice are scavengers, feeding on skin and other debris found on the host's body, but some species feed on sebaceous secretions and blood. Image courtesy of US Centers for Disease Control and Prevention.

See When Bugs Feast: What's Causing that Itch?, a Critical Images slideshow, to help identify various skin reactions, recognize potential comorbidities, and select treatment options.

Differentiating between insect bites and stings

Many patients confuse an insect bite with a sting and may use the terms interchangeably. A bite is usually from mouth parts and occurs when an insect is agitated to defend itself or when an insect seeks to feed. Bites from mosquitoes, fleas, bed bugs, and mites are more likely to cause itching than pain.

See the image below.


Anopheles albimanus mosquito feeding on human hos Anopheles albimanus mosquito feeding on human host. Image courtesy of US Centers for Disease Control and Prevention.
The Oriental rat flea (Xenopsylla cheopis). Image The Oriental rat flea (Xenopsylla cheopis). Image courtesy of US Centers for Disease Control and Prevention.

A stinging apparatus is usually a sharp organ of offense or defense, especially when connected with a venom gland, and adapted to inflict a wound by piercing, as the caudal sting of a scorpion. The stinger is typically located at the rear of the animal. Animals with a stinger include bees, wasps, hornets, and scorpions.

Hymenoptera [1]

Most stinging insects are of the order Hymenoptera, which is made up of multiple families, including 3 that are clinically important: Apidae (bees), Vespidae (wasps), and Formicidae (ants). Bees have barbed stingers that disengage, causing them to die after a single sting. Wasps, hornets, and yellow jackets (Vespidae family members) do not have barbed stingers and, as such, can sting multiple times.[2]

See the image below.

Yellow jacket wasp. Image courtesy of US Centers f Yellow jacket wasp. Image courtesy of US Centers for Disease Control and Prevention.

Since their introduction into the southern United States in the 1920s, imported fire ants anchor themselves with their mandibles and subsequently inflict a sting. Fire ants often pivot or re-anchor themselves only to sting again and again resulting in a sensation of fire at the site. When fire ants swarm, they often position themselves on their victim and sting simultaneously in response to an alarm pheromone released by one or several individuals. The response is very aggressive and results in cutaneous pustule formation from formic acid deposition.  Immobilized or elderly patients can become rapidly covered by swarms of these ants, resulting in severe stings and even death (See Fire Ant Bites).

Fire ant (Solenopsis invicta). Image courtesy of W Fire ant (Solenopsis invicta). Image courtesy of Wikimedia Commons.

Hymenoptera stings result in more fatalities than stings or bites from any other arthropod.

Bites by classes Insecta

This article is limited to bites by insects and not arachnids. Stings by members of the order Hymenoptera and order Scorpionida are discussed in other articles, as are bites of venomous arachnids in the class Arachnida (spiders) and bites of the order Acarina (mites and ticks).

Injuries from exposure to millipedes (class Diplopoda), centipedes (class Chilopoda), and caterpillars (order Lepidoptera) also are discussed in other articles (see Differentials); however, many of the principles that guide diagnosis and treatment of insect bites also apply to bites and stings of these other organisms.

Bed bugs [3]

Bed bugs (Cimex lectularius) were essentially a nonissue in the 1970s and 1980s, owing to effective insecticides like DDT. Increasing resistance and limitation of those insecticides have caused bed bug infestations to become an almost ubiquitous issue in the United States and other developed countries. A multitude of studies have shown an alarming increase of bed bug infestations over the last several years.[4] Bed bugs tuck away in clothing and shoes or easily migrate through walls of shared housing. Bed bugs can usually be found initially in the inner workings or the base of box springs but also like to hide in mattresses, under baseboards, along crevices in the walls, in vents, and even behind picture frames.[4] Infestations can be identified by fecal spotting (seen below).

Fecal staining from bed bugs in the crevice of a m Fecal staining from bed bugs in the crevice of a mattress. © 2014 Australian Family Physician. Reproduced with permission from The Royal Australian College of General Practitioners (RACGP), published in Doggett SL, Russell R. Bed bugs - What the GP needs to know. Aust Fam Physician. Nov 2009;38(11):880-4.

Bed bugs are flightless and are ovoid and flattened in shape. They are photophobic and all are obligatory blood feeders on vertebrates, with their preferred host being humans. Bed bugs have 5 juvenile stages, which are pictured below, along with the adult male and female forms.[5]

When bitten, cutaneous reactions (as seen below) usually appear within several hours of the bite, and patients usually notice these reactions the morning after having been bitten.

Various stages of the bed bug life cycle. © 2014 A Various stages of the bed bug life cycle. © 2014 Australian Family Physician. Reproduced with permission from The Royal Australian College of General Practitioners (RACGP), published in Doggett SL, Russell R. Bed bugs - What the GP needs to know. Aust Fam Physician. Nov 2009;38(11):880-4.

The reactions themselves are myriad in character and vary widely between individuals, with some patients showing no reaction at all.[5] Distinguishing a bed bug lesion from those caused by other insects is difficult; however, the classic "bed bug wheal" is an extremely pruritic papular urticaria and may be as large as 2-6 cm. For the clinician, the history of bug or insect bites may be unknown to the patient and this should always be in the differential, especially in the setting of a new travel location for sleep or worsening lesions just after sleep. These lesions can be in linear or bunched configurations and are usually found on exposed skin.[5] Other cutaneous reactions can be more pronounced, with anything from bullous, hemorrhagic reaction[6] to a more targetoid appearance.[7] Anaphylaxis from bed bug bites is also possible, necessitating prompt recognition and treatment.

See the image below.

Typical bed bug rash. Image courtesy of Wikimedia Typical bed bug rash. Image courtesy of Wikimedia Commons.

Treatment of cutaneous reactions does not differ from the general treatment for other insect envenomations discussed later. Although difficult, identifying cutaneous lesions from bed bugs versus other causes is important to prevent misdiagnosis and subsequent unneeded treatments and procedures (eg, scabicides, skin biopsies). Bed bugs are not known to transmit any human diseases.[4] Eradication of bed bug harborages is expensive, specialized, and challenging to say the least. It should only be undertaken by professionals.

Exotic insects

Although illness related to insect exposure in a particular locale may be easily recognizable, the emergency physician must also be aware of more exotic insect-related diseases as humans travel to more remote areas of the country and the world. Additionally, exotic insects are often kept as pets (sometimes illegally) or can be encountered in shipments of foreign origin (eg, mantises, stick insects).

Anaphylactic shock

Anaphylactic shock is the most notable immediate risk associated with insect exposures. Hypersensitivity to otherwise harmless insect saliva, venom, body parts, excretions, or secretions can cause systemic responses in some individuals. Diagnosing the early phases of a systemic allergic reaction preceding anaphylactic shock is of paramount importance in treating any patient in whom insect exposure is suspected. Severe anaphylaxis can be fatal in as little as 10 minutes.

The reoccurrence rate is 40-60% for insect stings. Hence, the patient should be instructed on how to avoid future exposure to the causative agent, if possible. A prescription and clear instructions on the use of an epinephrine autoinjector should be provided to patients when the risk of another reaction is judged to be substantial.[8]

Diseases transmitted by insect bites

The need to be aware of diseases transmitted by insect bites is crucial; Lyme disease, transmitted by ticks, and malaria, transmitted by mosquitoes, are discussed in other articles (see Tick-borne Diseases, Lyme; Malaria).

Chagas disease, increasingly found in the desert southwest and in persons residing in or traveling to Central America or South America, should be considered, particularly when the bite site is on the soft skin of the periorbita or lips.[9] The kissing bug (see below) can be a vector for this infection. Because this infection may produce an acute and chronic illness with notable morbidity and mortality, especially in pediatric patients, clinicians should maintain a high index of suspicion (see Trypanosomiasis).

Kissing bug (Triatoma sanguisuga) can be a vector Kissing bug (Triatoma sanguisuga) can be a vector for Chagas disease. Image courtesy of US Centers for Disease Control and Prevention.

Mosquito and tick-borne encephalitides such as those produced by the eastern equine virus or the West Nile virus also should be considered in patients presenting with meningismus (see Encephalitis).

Of note, some illnesses transmitted by insects do not produce symptoms until long after the infecting bite. In South America and parts of Africa, blackflies (Simuliidae) are responsible for transmission of onchocerciasis. This illness is also known as river blindness and eventually can produce blindness years after the initial infection. This disease is extremely rare in the United States. Chagas disease, a leading cause of cardiomyopathy in the world, may present latently as well. Obtaining a history of international travel is important because this information can lead to a diagnosis that would otherwise be overlooked. Determining the destination, time of year, length of stay, and time since travel are all important pieces of history to obtain.

Exposure to arthropods may produce dermatitis, cellulitis, urticaria, or blistering unrelated to biting or stinging. Some species of moths, caterpillars, centipedes, beetles, and spiders have urticating hairs or secretions that can cause cutaneous irritation. For further information, please refer to the respective articles on these exposures (see Differentials).

An uncommon occurrence in North America is myiasis by fly larvae. Fly larvae enter the host through varying mechanisms ranging from oviposition of live, burrowing larvae on the host, on or near open wounds, to attachment to other bloodsucking insects. While not generally the result of an insect bite, myiasis can produce pustules and lesions similar to insect bites. These lesions generally contain one or more developing fly larvae. Severe cases of myiasis can cause seizures.

Plant-eating phytophagous insects can bite in self-defense, and their bites are not predatory. This article is limited to discussion of organisms that bite to feed on blood or to catch prey.

Relatively harmless insects

Cockroaches have been reported to bite humans, but their bite generally is harmless. Continued repeated exposure to their remains and feces poses a greater health threat, such as increased incidence of asthma, especially in inner cities, and their remains and feces are possible vectors for transmission of viral and bacterial diseases.

Earwigs generally are harmless insects that have earned an unpleasant reputation. This may be because of their depiction in popular culture, such as in the television series, "The Night Gallery." Although they appear to have a large pincer on the posterior abdomen, it is not capable of rendering anything more serious than a mild pinch. Additionally, and contrary to popular belief, they do not routinely enter the human ear canal and parasitize humans. Cockroaches are much more likely to be found lodged in a patient's auditory passage.

Pathophysiology

Mouthparts of biting insects can be classified into 3 broad groups: piercing, sponging, and biting. Tremendous diversity exists in the morphology of these groups. Insects discussed in this article generally are nonvenomous, yet many species inject saliva while biting. Their saliva may aid in digestion, inhibit coagulation, increase blood flow to the bite, or anesthetize the bite locus. Most lesions are the result of the victim's immune response to these insect secretions. In the case of Chagas disease, the infective organism is transmitted via the feces of a reduviid bug, which enters through the bite site when the wound becomes pruritic and is scratched. Most insect bites are minor and can result in superficial puncture wounds to the skin. Horseflies feed with a large scissorlike proboscis that can cause a relatively deep and painful wound.

Epidemiology

Frequency

United States

In the United States, the American Association of Poison Control Centers (AAPCC) reported 8,983 cases of single exposures to insects in 2016.[10] Approximately 590 of these were listed as resulting in moderate reactions and 16 serious reactions. A moderate reaction is defined as signs or symptoms that were more pronounced or systemic, whereas a major reaction is life-threatening or leads to significant residual disability. It is important to understand that the numbers mentioned in this report are only those reported to American Poison Centers, and it should be of no surprise that the actual numbers of uncaptured data are much higher. Fatalities among these exposures are rarely reported to poison centers and usually result from allergic reactions to Hymenoptera stings. Because of underreporting, these numbers are only a glimpse as to what is actually occurring.[10]

The AAPCC 2016 Annual Report published the following single-incident exposures for insects[10] :

  • Ant or fire ant bites: 578 total; 28 moderate, 1 major, 0 deaths

  • Bee, wasp, or hornet stings: 3,348 total; 269 moderate, 11 major, 3 deaths

  • Mosquitos: 178 total; 8 moderate, 0 major, 0 deaths

  • Other insect bites and/or stings: 4,879 total; 268 moderate, 4 major, 0 deaths

International

Reliable statistics are not available for insect bite exposures because most cases are not reported and do not require hospital care.[11] A study in tropical Zimbabwe, where biting insects are common, found that 1.5% of hospital admissions were related to insect exposure, including both bites and stings. A vast majority of these were arachnid or Hymenoptera related.

Race

No race predilection is known.

Sex

No sex predilection is known.

Age

No age predilection is known.

Prognosis

Prognosis generally is good except in patients with severe untreated anaphylaxis or in those with chronic or invasive infections.

Mortality associated with insect bites is from hypersensitivity reactions, either anaphylactic (immunoglobulin E [IgE] mediated) or anaphylactoid (non-IgE mediated), or from complications resulting from infection. The US Centers for Disease Control and Prevention estimates an annual rate of 90-100 deaths from insect venom anaphylaxis.[12] In patients with anaphylaxis secondary to insect venom, risk factors for increased severity of reaction include older age, preexisting cardiovascular disease or mast cell disorder, concomitant treatment with beta-adrenergic blockage or ACE inhibitors, previous severe reactions, and the type of insect (honeybees presenting the highest risk).[13]

Patient Education

Biting insects are ubiquitous in nearly all parts of the world, yet certain measures can be taken to minimize risk of exposure. Periodic pest control may eliminate nests and minimize reproduction of biting insects.

Wear protective clothing (ie, long pants, long sleeves), especially when outdoors. Many insects are incapable of biting through clothing. Additionally, light-colored clothing appears to be less attractive to many biting insects, including mosquitos.[14] Avoid dark colors or brightly colored floral patterns. Wear protective footwear. Wear gloves when working with soil or in areas of heavy infestation.

Avoid use of heavy perfumes, scented soaps, sprays, or lotions that may attract insects. Be aware of surroundings; for example, avoid dense vegetation or animals suspected of carrying fleas, chiggers, or ticks. Prudent use of insect repellent can help minimize exposure to insect bites and stings.[15] Be aware of the potential for bees or other foraging insects to enter opened soft drink containers that are left idle.

For a guide to recognizing common stinging hymenoptera, please see this CDC pictorial guide.

For a guide to recognizing common scorpion species in the United States, please see the CDC pictorial key to common US scorpion species.

For patient education resources, see the First Aid and Injuries Center. Also see the patient education articles Insect Bites, Allergy: Insect Sting, Severe Allergic Reaction (Anaphylactic Shock), Black Widow Spider Bite, Brown Recluse Spider Bite, and Ticks.

 

Presentation

History

Most patients are aware of insect bites when they occur or shortly thereafter, but because it is such a common occurrence, the exposure is typically dismissed unless a severe or systemic reaction occurs.

Reactions to bites may be delayed due to the host being asleep or because the saliva of some micropredators may contain an anesthetic secreted to allow uninterrupted blood-feeding.

Patients who present with a history of homelessness or of staying in homeless shelters may have an exposure to organisms such as bedbugs.[4, 16, 17] Alternatively, patients with impairment from mental illness may also be susceptible to infestation with insect parasites.

Exposure to feral animals or even to domesticated animals, such as livestock or house pets, may predispose patients to exposure to biting insects such as fleas, bedbugs,[4, 18, 17] or lice.

Types of reactions

In a local reaction, the patient may complain of discomfort, itching, moderate or severe pain, erythema, tenderness, warmth, and edema of tissues surrounding the site. Although it may involve neighboring joints, local reactions cause no systemic symptoms.

In a severe local reaction, complaints include generalized erythema, urticaria, and pruritic edema. Severe local reactions increase the likelihood of serious systemic reactions if the patient is exposed again at a later time.

In a systemic or anaphylactic reaction, the patient may complain of localized symptoms as well as symptoms not contiguous with the bite location. Symptoms can range from mild to fatal. Early complaints typically include generalized rash, urticaria, pruritus, and angioedema. These symptoms may progress, and the patient may develop anxiety, disorientation, weakness, gastrointestinal disturbances (eg, cramping, diarrhea, vomiting), uterine cramping in women, urinary or fecal incontinence, dizziness, syncope, hypotension, stridor, dyspnea, or cough. As the reaction progresses, patients may experience respiratory failure and cardiovascular collapse.[19]

Delayed reactions may appear 10-14 days after a sting. Symptoms of delayed reactions resemble serum sickness and include fever, malaise, headache, urticaria, lymphadenopathy, and polyarthritis.

Physical Examination

Without a clear patient history, diagnosis of an insect bite can be difficult since the initial response may be limited to erythema, local pain, pruritus, or edema.

Wheals and urticaria are common initial signs and generally appear within a few minutes of the bite. Unfortunately, many dermatologic conditions also produce similar cutaneous signs and may confound the diagnosis.

Identification of the insect responsible for the bite may be possible by examining the location, number, pattern, and sequelae of the bite(s).

Clinical criteria for diagnosis of anaphylaxis according to the World Allergy Organization are shown in the image below.

Insect Bites. World Allergy Organization anaphylax Insect Bites. World Allergy Organization anaphylaxis pocket card. Reprinted from The Journal of Allergy and Clinical Immunology, Vol 127, Issue 3, Simons FER et al, World Allergy Organization anaphylaxis guidelines; Summary, Pgs 587-93, March 2011, with permission from Elsevier. Available at http://www.jacionline.org/article/S0091-6749(11)00128-X/fulltext.
 

DDx

 

Workup

Laboratory Studies

Laboratory studies are seldom necessary. Appropriate laboratory studies should be ordered if the patient is compromised severely and requires hospital admission or end-organ failure is suspected, or for evaluation of secondary complications such as cellulitis.

Biopsy of lesions generally is nondeterminant and is impractical in the ED.

Microscopic examination of skin scrapings can be useful in the diagnosis of scabies or mite infestations but are not useful for most insect bites.

Serology studies may be useful in determining infection due to an insect vector, but these are not available in the ED and may take weeks to obtain a result.

 

Treatment

Prehospital Care

For a large local reaction, ice packs may minimize swelling. Apply ice for no more than 15 minutes at a time using a cloth barrier between ice and skin to prevent direct thermal injury to the skin.

Epinephrine is the mainstay of prehospital treatment of a systemic reaction; the route of administration (subcutaneous, intramuscular, intravenous [IV], endotracheal) depends on the patient's condition and the expertise of the prehospital provider. Systemic antihistamines and corticosteroids, if available, help manage systemic reactions. Many patients who are allergic to stings carry commercially available bee sting kits containing an autoinjector of epinephrine. Refer to Hymenoptera Stings.

Topical antihistamines should not be applied over large surface areas, and they should not be used concurrently with systemic H1 antihistamines. Systemic anticholinergic toxicity may result from misuse of these medications.

Use of H2-blocking drugs (usually used to reduce gastric acid secretion) may be used concurrently with H1-blocking antihistamines.

In many patients, transport to a hospital is not necessary. Those requiring transport include patients who develop signs or symptoms of a systemic response or individuals with a history of insect-related anaphylaxis. A phone call to the regional poison center may save a costly visit to the ED.

Regarding stings, refer to Hymenoptera Stings for complete information; however, note that if the bee stinger is present in the wound, it should be removed. Although conventional teaching suggested scraping the stinger out to avoid squeezing remaining venom from the retained venom gland into the victim, involuntary muscle contraction of the gland continues after evisceration and the venom contents are quickly exhausted. Immediate removal is the important principle and the method of removal is irrelevant.

Emergency Department Care

Endotracheal intubation and ventilatory support may be required for severe anaphylaxis or angioedema involving the airway.

Treat emergent anaphylaxis in an atopic individual with an initial intramuscular injection of 0.3-0.5 mL of 1:1000 epinephrine. This may be repeated every 10 minutes as needed. Note that insect bites only rarely cause anaphylaxis compared with stings; refer to Hymenoptera Stings.

A bolus of IV epinephrine (1:10,000) may be used cautiously in severe cases. Solution of 1:10,000 typically is found in 10-mL vials. Repeated 1-mL doses are a reasonable initial approach in a critically ill patient with anaphylaxis. Once a positive response is achieved, these boluses can be followed by a carefully monitored, continuous epinephrine infusion. Use extra care in monitoring formulation, concentration, and dose when administering IV epinephrine to avoid inadvertent overdose.

Severely hypotensive patients may require a large volume of IV fluids. Monitor for angioedema and pulmonary edema.

Antihistamines, both H1 and H2 blockers, are useful in treating systemic reactions. Diphenhydramine is commonly used in the emergency department, but cetirizine should also be considered in patients not requiring intravenous medications, as it is equally efficacious, has a similar onset of action, and has a longer duration. Corticosteroids also are often used in such patients.

Refer to Anaphylaxis and Serum Sickness for further guidance.

Ensure appropriate tetanus prophylaxis.

Undefined erythema and swelling seen may be difficult to distinguish from cellulitis. As a general rule, infection is present in a minority of cases and antibiotic prophylaxis is not recommended.

Related diagnostic and treatment guidelines are available on anaphylaxis, travel medicine, and referral guidelines (also see Further Reading).[20, 21, 22]

Further inpatient care

Patients with true anaphylaxis, particularly if associated with hypotension, often are admitted for monitoring or observation in the ED upon recovery. Accepted definition of "true" anaphylaxis requires the involvement of at least 2 of the following 4 systems: cardiovascular, gastrointestinal, skin, or respiratory; although newer guidelines indicate that hypotension only may be present after exposure to a known trigger.[13] Literature provides no clear direction on who needs admission. Certain patients with a disease transmission (eg, malaria) may require admission.

Corticosteroids and antihistamines usually are continued for a few (3-4) days after a systemic response. Serum sickness reactions may require longer therapy (see Serum Sickness).

Consultations

In cases in which determining the insect species is important, a health department, agriculture extension, or university entomologist may be useful.

In cases of potential vector-borne disease transmission, an infectious disease specialist may be of help.

If the potential infection is associated with travel to a tropical region, consider contacting a tropical medicine specialist or the Centers for Disease Control and Prevention (CDC) at 1-877-394-8747 (Traveler's Health Hotline).

A regional poison center may be of assistance in difficult or complicated cases or for general information.

Complications

Secondary infection may result from an insect bite.

Symptoms of disease transmitted by insect bites may not be evident for days, weeks, or even longer.

Pregnancy and anaphylaxis

Studies on treatment of anaphylaxis in pregnancy are primarily based in the obstetric literature and generally are case reports dealing with hymenopteran stings. Again, many patients confuse an insect bite with a sting and may use the terms interchangeably. The following adverse outcomes have been reported in case reports following hymenoptera envenomation during pregnancy and are included in this article because of their importance[23] :

  • Preterm delivery occurred at 35 weeks' gestation despite tocolysis and cerclage and attributed to a "postanaphylactic reaction" from a wasp sting.

  • A woman aged 31 years developed severe anaphylaxis after bee sting at 30 weeks' gestation. Preterm labor occurred at 35 weeks' gestation, and the infant was found to be cyanotic and hypotonic. The infant died at age 65 days, and the cause of death was determined to be encephalomalacia from maternal anaphylaxis.

  • A woman aged 21 years at 40 weeks' gestation developed severe anaphylaxis from an ant sting and then developed placental abruption and intrauterine death 16 hours later. This was tentatively attributed to the anaphylactic response and epinephrine administration.[23]

All patients who have had significant or systemic reactions to Hymenoptera envenomations in the past should consider venom immunotherapy as an outpatient, because it is well tested, highly effective at preventing future reactions, and widely available.[23] Pregnant females are not usually initiated on this therapy secondary to lack of safety data, but they can consider continuation of therapy begun prior to impregnation. However, preterm labor has been reported in several cases dealing with this population. Otherwise, standard supportive care should be taken for cutaneous Hymenoptera envenomations.[23] Anaphylaxis should be promptly recognized and treated in the standard fashion. Fetal data are limited but the adage "what is good for the mother is good for the fetus" may well also apply to anaphylaxis.

See Hymenoptera Stings.

Long-Term Monitoring

Follow-up monitoring for infection is advised for individuals bitten by an insect known to transmit a secondary disease, if exposed to the vector in an endemic area (eg, Chagas disease in the case of kissing bugs [Reduviidae][24, 25] ).

Individuals who recover from a systemic reaction should consult with an allergist regarding desensitization and prevention measures.

Prescribe epinephrine auto-injector prior to discharge if the patient had a systemic response to an envenomation (see Hymenoptera Stings). Some patients require more than one injection of epinephrine to treat anaphylaxis, so prescribing two injectors should be considered.[26]

 

Medication

Medication Summary

Goals of therapy are to treat anaphylaxis and prevent complications.

Cardiovascular agents

Class Summary

These agents act to decrease the muscle tone in the small and large pulmonary airways and increase vascular tone.

Epinephrine (Adrenalin, Bronitin, EpiPen)

Epinephrine is the drug of choice for shock, angioedema, airway obstruction, bronchospasm, and urticaria in severe anaphylactic reactions. Administer IM; administer IV to patients in extremis, It may be administered SL or ET when no IV access is available. Continuous infusion may be given in cases of refractory shock.

Bronchodilators

Class Summary

Through activation of cyclic adenosine monophosphate (cAMP), beta agonists stimulate the ATPase pump, thereby shifting potassium into the intracellular compartment and stimulating an adrenergic response.

Albuterol (Ventolin)

Albuterol is a beta agonist useful in treating bronchospasms refractory to epinephrine. It relaxes bronchial smooth muscle by action on beta2 receptors and has little effect on cardiac muscle contractility. Numerous inhaled beta agonists are used for treatment of bronchospasm; albuterol is used most commonly.

Antihistamines

Class Summary

These agents prevent histamine response in sensory nerve endings and blood vessels; they are more effective in preventing histamine response than in reversing it. H2 antihistamines are useful in treatment of anaphylactic reactions when used concomitantly with H1 antagonists. Many H2 blockers are available. Cimetidine is the prototype drug.

Diphenhydramine (Benadryl)

Diphenhydramine is used for symptomatic relief of allergic symptoms caused by histamines released in response to allergens. There are many effective H1 blockers; diphenhydramine is effective and widely available.

Cimetidine (Tagamet)

Cimetidine is an H2 antagonist that, when combined with H1 type, may be useful to treat itching and flushing in anaphylaxis, pruritus, urticaria, and contact dermatitis that do not respond to H1 antagonists alone. Use it in addition to H1 antihistamines.

Corticosteroid, Systemic

Class Summary

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. In addition, these agents modify the body's immune response to diverse stimuli. Prednisone and methylprednisolone are typical drugs of this class. Oral bioavailability is generally similar to parenteral; administer oral prednisone when indicated if a patient is not in extremis and can comfortably take it orally; administer parenteral steroids when indicated for a patient in more severe circumstances.

Prednisone

Prednisone is believed to ameliorate delayed effects of anaphylactic reactions and may limit biphasic anaphylaxis. Doses are general guidelines for usage; dosing is highly individualized.

Methylprednisolone (Solu-Medrol, Depo-Medrol)

Methylprednisolone is useful for treating inflammatory and allergic reactions. By reversing increased capillary permeability and suppressing PMN activity, it may decrease inflammation. A multitude of corticosteroid preparations is available. Methylprednisolone is widely available in the ED because of its other uses (ie, acute asthma, spinal cord injury) and is supplied in both parenteral and oral formulations.

Toxoids

Class Summary

These are used for active immunity against tetanus.

Tetanus toxoid adsorbed or fluid

Tetanus toxoid adsorbed or fluid is used to induce active immunity against tetanus in selected patients. The immunizing agents of choice for most adults and children older than 7 years are tetanus and diphtheria toxoids. It is necessary to administer booster doses to maintain tetanus immunity throughout life.

Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen-containing product.

In children and adults, it may be administered into deltoid or midlateral thigh muscles. In infants, the preferred site of administration is the mid thigh laterally.

Immunoglobulins

Class Summary

These consist of immunoglobulins pooled from serum of immunized patients.

Tetanus immune globulin (TIG)

Tetanus immune globulin is used for passive immunization of any person with a wound that may be contaminated with tetanus spores.

 

Questions & Answers

Overview

What are the clinical implications of insect bites?

What is the difference between insect bites and stings?

What are the clinical manifestations of bites from bed bugs and how are they treated?

What is the most serious initial reaction to insect exposures?

Which diseases are transmitted by insect bites?

What are the health risks of cockroach and earwig exposures?

What is the pathophysiology of insect bites?

What is the incidence of insect bites in the US?

What is the global prevalence of insect bites?

What are racial predilections of insect bites?

What are sex-related predilections of insect bites?

Which age group has the highest incidence of insect bites?

What is the prognosis of insect bites?

What should be included in the patient information about insect bites?

Presentation

Which clinical history findings are characteristic of insect bites?

What are the signs and symptoms of insect bites?

Which physical findings are characteristic of insect bites?

DDX

What are the differential diagnoses for Insect Bites?

Workup

What is the role of lab testing in the diagnosis of insect bites?

Treatment

What is included in prehospital care for insect bites?

What is included in emergency department (ED) care for insect bites?

When is hospitalization indicated for the treatment for insect bites?

Which specialist consultations are beneficial for patients with insect bites?

What are complications of insect bites?

What are complications of insect bites during pregnancy?

What is the role of venom immunotherapy in the treatment of insect bites?

What is included in the long-term monitoring of patients treated for insect bites?

Medications

What is the goal of therapy for insect bites?

Which medications in the drug class Immunoglobulins are used in the treatment of Insect Bites?

Which medications in the drug class Toxoids are used in the treatment of Insect Bites?

Which medications in the drug class Corticosteroid, Systemic are used in the treatment of Insect Bites?

Which medications in the drug class Antihistamines are used in the treatment of Insect Bites?

Which medications in the drug class Bronchodilators are used in the treatment of Insect Bites?

Which medications in the drug class Cardiovascular agents are used in the treatment of Insect Bites?