- Author: Henry K Wong, MD, PhD; Chief Editor: Dirk M Elston, MD more...
Urticaria, commonly referred to as hives, appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very pruritic (see the image below). It may be acute (<6 wk) or chronic (>6 wk). Urticaria may be confused with a variety of other dermatologic diseases that are similar in appearance and are also pruritic; usually, however, it can be distinguished from these diseases by an experienced clinician.
Signs and symptoms
Information regarding history of previous urticaria and duration of rash and itching is useful for categorizing urticaria as acute, recurrent, or chronic. For chronic or recurrent urticaria, important considerations include previous causative factors and the effectiveness of various treatments, as follows :
Precipitants, such as heat, cold, pressure, exercise, sunlight, emotional stress, or chronic medical conditions
Other medical conditions that can cause pruritus (usually without rash), such as diabetes mellitus, chronic renal insufficiency, primary biliary cirrhosis, or other nonurticarial dermatologic disorders
Family and personal medical history of angioedema - Characteristics of angioedema  include vasodilation and exudation of plasma into the deeper tissues more so than with simple urticaria; angioedema can occur with and without the wheals of simple urticaria and presents clinically as subcutaneous swelling that is generally nonpitting and nonpruritic; it can affect the mouth as well as the mucosal surfaces of the respiratory and GI tracts, manifesting as hoarseness and GI upset; it can be a feature of anaphylaxis if the throat is involved, leading to airway compromise
For acute urticaria, the main consideration involves possible precipitants, such as the following :
IV radiocontrast media
New perfumes, hair dyes, detergents, lotions, creams, or clothes
Exposure to new pets (dander), dust, mold, chemicals, or plants
Pregnancy (usually occurs in last trimester and typically resolves spontaneously soon after delivery)
Contact with nickel, rubber, latex, industrial chemicals, and nail polish
Sun or cold exposure
Alcohol ingestion 
Physicall urticaria is characterized by the following:
Blanchable, raised, palpable wheals, which can be linear, annular (circular), or arcuate (serpiginous); can occur on any skin area; are usually transient and migratory; and may coalesce rapidly to form large areas of erythematous, raised lesions that blanch with pressure
Dermographism or dermatographism (urticarial lesions resulting from light scratching)
The physical examination should focus on conditions that might precipitate urticaria or could be potentially life-threatening and include the following :
Angioedema of the lips, tongue, or larynx
Individual urticarial lesions that are painful, long-lasting (>24 h), or ecchymotic or that leave residual hyperpigmentation or ecchymosis upon resolution are suggestive of urticarial vasculitis
Systemic signs or symptoms
Scleral icterus, hepatic enlargement, or tenderness
Pneumonia or bronchospasm (asthma)
Cutaneous evidence of bacterial or fungal infection
See Clinical Presentation for more detail.
Laboratory studies may be helpful, as follows:
Acute urticaria (<6 wk) - Laboratory studies generally are not indicated
Chronic or recurrent urticaria (>6 wk) - Basic laboratory studies should include complete blood count (CBC), erythrocyte sedimentation rate (ESR), thyroid-stimulating hormone (TSH), and antinuclear antibody (ANA) 
Other studies that may be considered include the following:
Imaging studies - Generally not indicated unless suggested by a specific symptom or sign 
Punch biopsy - If urticarial vasculitis is suspected
See Workup for more detail.
Acute urticaria may rarely progress to life-threatening angioedema or anaphylactic shock in a very short period, although anaphylactic shock is usually of rapid onset with no urticaria or angioedema. Prehospital measures may include the following when there is concern for anaphylactic shock:
If associated angioedema is present, IM epinephrine
If associated bronchospasm is present, nebulized albuterol
Other measures may be appropriate, such as continuous ECG, blood pressure and pulse oximetry monitoring; administering intravenous crystalloids if the patient is hypotensive; and administering oxygen.
Diphenhydramine or hydroxyzine, if available
Management of urticaria is focused on treating the symptoms and typically is not altered by underlying etiology. The mainstay is avoidance of further exposure to the antigen causing urticaria. Pharmacologic treatment options include the following:
Antihistamines, primarily those that block H1 receptors with low sedating activity, such as fexofenadine, loratadine, desloratadine, cetirizine, and levocetirizine are first-line therapy [6, 7] ; these are preferred over diphenhydramine and hydroxyzine; H2 antihistamines, such as cimetidine, famotidine, and ranitidine, may have a role when used in combination with H1 antihistamines, although the benefit is unclear 
Epinephrine (controversial in acute urticaria)
Methotrexate, colchicine, dapsone, indomethacin, and hydroxychloroquine (for urticarial vasculitis) 
Patients with chronic or recurrent urticaria should be referred to a dermatologist for further evaluation and management.
Consultation with or referral to a dermatologist, allergist, immunologist, or rheumatologist may be appropriate in selected cases, particularly in cases of complicated, recurrent, refractory, severe, or chronic urticaria. Dermatology referral is mandatory if urticarial vasculitis is suspected.
See Treatment and Medication for more detail.
Urticaria, commonly referred to as hives, is the most frequent dermatologic disorder seen in the emergency department (ED). It appears as raised, well-circumscribed areas of erythema and edema involving the dermis and epidermis that are very pruritic. Urticaria may be acute (lasting <6 wk) or chronic (lasting >6 wk). A large variety of urticaria variants exist, including acute immunoglobulin E (IgE)–mediated urticaria, chemical-induced urticaria (non-IgE-mediated), autoimmune urticaria, cholinergic urticaria, cold urticaria, mastocytosis, periodic fever syndromes including Muckle-Wells syndrome, and many others.[2, 10] While acute urticaria is generally related to an exogenous allergen or acute infection, chronic urticaria is more likely to be associated with autoimmunity.[8, 11, 12]
Urticaria may be confused with a variety of other dermatologic diseases that are similar in appearance and are pruritic including atopic dermatitis (eczema), maculopapular drug eruptions, contact dermatitis, insect bites, erythema multiforme, pityriasis rosea, urticarial vasculitis, and others. Usually, however, the experienced clinician is able to distinguish urticaria from its mimickers owing to its distinctive appearance (see the images below), intensely pruritic nature, and complete blanching with pressure.
Acute urticaria is most often a benign, self-limited skin disease. It usually occurs independently, but it may contribute to the more serious clinical manifestations of anaphylaxis: angioedema and anaphylactic shock. The etiologies of both acute and chronic urticaria are numerous (see Causes in Presentation). The etiologic agent is more likely to be identified in acute urticaria (40-60%) than in chronic urticaria (10-20%). The lesions of IgE-mediated urticaria usually last less than 24 hours and are often migratory, leaving no residual skin abnormalities. The lesions of urticarial vasculitis usually last longer, classically, but not always, longer than 24 hours. They are both painful and pruritic and often leave purpuric and hyperpigmented lesions. Unlike simple urticaria, urticarial vasculitis demonstrates leukocytoclastic vasculitis on histology. Like urticaria, it may occur with or without angioedema. It may be associated with systemic symptoms such as arthralgias and GI symptoms, which are more common in patients with low complement levels. Although it is most often idiopathic, it is more often associated with autoimmune diseases such as lupus and Sjögren syndrome, as well as viral infections, medications, and malignancy, when compared with classic urticaria. If urticarial vasculitis is suspected, an autoimmune screen, including complement levels, should be included in the workup. Initial treatment options include antihistamines and NSAIDs.
For more information, see Medscape's Allergy Resource Center.
Urticaria results from the release of histamine, bradykinin, leukotriene C4, prostaglandin D2, and other vasoactive substances from mast cells and basophils in the dermis. These substances cause extravasation of fluid into the dermis, leading to the urticarial lesion. The intense pruritus of urticaria is a result of histamine released into the dermis. Histamine is the ligand for two membrane-bound receptors, the H1 and H2 receptors, which are present on many cell types. The activation of the H1 histamine receptors on endothelial and smooth muscle cells leads to increased capillary permeability. The activation of the H2 histamine receptors leads to arteriolar and venule vasodilation.[14, 15]
This process is caused by several mechanisms. The type I allergic IgE response is initiated by antigen-mediated IgE immune complexes that bind and cross-link Fc receptors on the surface of mast cells and basophils, thus causing degranulation with histamine release. The type II allergic response is mediated by cytotoxic T cells, causing deposits of immunoglobulins, complement, and fibrin around blood vessels. This leads to urticarial vasculitis. The type III immune-complex disease is associated with systemic lupus erythematosus and other autoimmune diseases that cause urticaria.
Complement-mediated urticarias include viral and bacterial infections, serum sickness, and transfusion reactions. Urticarial transfusion reactions occur when allergenic substances in the plasma of the donated blood product react with preexisting IgE antibodies in the recipient. Certain drugs (opioids, vecuronium, succinylcholine, vancomycin, and others) as well as radiocontrast agents cause urticaria due to mast cell degranulation through a non—IgE-mediated mechanism. Urticaria from nonsteroidal anti-inflammatory drugs may be IgE-mediated or due to mast cell degranulation, and there may be significant cross-reactivity among the nonsteroidal anti-inflammatory drugs (NSAIDs) in causing urticaria and anaphylaxis.
The physical urticarias in which some physical stimulus causes urticaria include immediate pressure urticaria, delayed pressure urticaria, cold urticaria, and cholinergic urticaria.[17, 18] For some urticarias, especially chronic urticarias, no cause can be found, despite exhaustive efforts—the so-called idiopathic urticarias, although most of these are chronic autoimmune urticaria as defined by a positive autologous serum skin test (ASST). This test is not specific for autoantibodies against a specific antigen or diagnostic of a specific disease state. To date, no reliable test exists to identify with certainty if chronic urticaria is autoimmune or nonautoimmune in the specific patient.[21, 22]
Acute urticaria affects 15-20% of the general population at some time during their lifetime. Chronic urticaria affects 2-3% of individuals over their lifetime.
The global frequency of urticaria is similar to that in the United States.
No variation in race is noted.
Incidence rates for acute urticaria are similar for men and women; chronic urticaria occurs more frequently in women (60%).
Urticaria can occur in any age group, although chronic urticaria is more common in the fourth and fifth decades.
Pruritus (itching) and rash are the primary manifestations of urticaria, and permanent hyperpigmentation or hypopigmentation is rare.
The prognosis in acute urticaria is excellent. Acute urticaria is usually self-limited, and individual lesions commonly resolve within 24 hours; however, episodes may recur for up to 6 weeks.
The prognosis in chronic urticaria is more guarded and depends on the comorbid disease causing the urticaria as well as the response to therapy. Chronic urticaria lasts more than 6 weeks.
Acute and chronic urticaria can result in severely impaired quality of life from pruritus and associated sleeplessness, as well as anxiety and depression. The depression can be severe enough to lead to suicide in rare cases. Additionally, many of the diseases associated with chronic urticaria may cause significant morbidity and mortality.
Education regarding avoidance of the suspected offending allergen is essential.
For patient education resources, see the Allergies Center and Skin Conditions and Beauty Center. Also see the patient education article Hives and Angioedema.
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