Immediate Hypersensitivity Reactions Treatment & Management

Treatment may vary depending on the type of allergic reaction. Some general observations are made below, but refer to articles on the specific topics for more details about treatment (eg, Anaphylaxis; Rhinitis, Allergic; Allergic and Environmental Asthma; Urticaria).

• Anaphylaxis

  • Assessment of the reaction is described as follows:
    • Withdraw the offending agent if applicable (eg, stop drug infusion).
    • Check the airway and secure if needed. Patients with respiratory compromise may need to be intubated. If laryngeal edema causes oral intubation to be difficult, a tracheostomy must be performed.
    • Assess the level of consciousness and vital signs.
  • Treatment is as follows:
    • Administer epinephrine immediately (see Medication).
    • Start intravenous fluids; these should be administered rapidly and as blood pressure and overall fluid status warrant.
    • Consider other vasopressors (eg, dopamine) if hypotension does not respond to the above measures. Norepinephrine may be used if dopamine is not effective. Importantly, isoproterenol should not be used because it is a peripheral vasodilator. Patients with beta-adrenergic blockade may be particularly difficult to treat. They have both chronotropic and inotropic cardiac suppression and may not respond to the above treatments. Glucagon has positive inotropic and chronotropic effects and is the drug of choice in these cases. Atropine can also be used but will only be effective in treating bradycardia.
    • H1- and H2-receptor blockers can be helpful in alleviating hypotension, pruritus, urticaria, rhinorrhea, and other symptoms. Cimetidine, when combined with any of several H1 antihistamines, has been demonstrated to block histamine-induced hypotension. Other H2 blockers have not been studied in this context.
    • Use albuterol nebulizers if needed.
    • Administer a corticosteroid, which is believed to help prevent or control the late-phase reaction.
    • Transfer the patient to the hospital for further observation and care.
    • Late phase reactions can occur 4-6 hours after the initial reaction and can be as severe as or worse than the original reaction. In some cases, late phase reactions can occur up to 36 hours later. Education of the patient and observation is, therefore, important.
  • Prevention is as follows:
    • Avoid the triggering allergen as much as possible.
    • Patients should be given a prescription for at least 2 autoinjectable epinephrine doses (eg, 2 EpiPens or 1 Twinject) and instructed in their proper use. Importantly, patients must carry them at all times.
    • Patients can also be instructed to carry both an H1 and an H2 antihistamine with them.
    • Patients must wear a Medic Alert type of bracelet to alert emergency responders to the possibility of anaphylaxis.
    • Patients should be taught what measures to take in case of a future anaphylactic reaction, ie, immediately administer epinephrine and take the antihistamine, call emergency services (eg, 911), or go to the nearest emergency department (even if feeling better after the epinephrine).
    • Specific allergen immunotherapy is highly effective in preventing anaphylaxis from hymenoptera stings and should always be considered for patients who have experienced a systemic reaction after an insect sting.
• Allergic rhinitis

  • Avoid the offending allergen, if possible.
  • Oral H1-receptor blockers are helpful for controlling itchiness, rhinorrhea, and lacrimation but most have little effect on nasal congestion.
  • Administer an intranasal glucocorticosteroid to control nasal symptoms, including nasal congestion. These medications need to be used regularly to be effective, and patients may need to use them for a week or more before maximum effect is seen.
  • Other topical nasal agents include azelastine and olopatadine (H1-receptor blockers) and cromolyn (a mast cell stabilizer).
  • Nasal azelastine and olopatadine have the advantage of treating rhinorrhea, nasal itchiness, sneezing, and also congestion. Azelastine has been shown to be helpful in treating both allergic and nonallergic vasomotor rhinitis. Nasal antihistamines have a rapid onset of action and can be used on an as-needed basis. Topical nasal decongestants can provide immediate relief of nasal congestion and can be used temporarily and as needed. Patients should be cautioned not to use them for more than a few days, however, as they can cause rebound congestion (rhinitis medicamentosa).
  • Topical decongestants, mast cell stabilizers, or antihistamines can be used for ocular symptoms; artificial tears might be helpful in mild cases, and this product can be refrigerated for an extra cooling effect. Cold compresses can also be used.
  • Again, use of topical decongestants should be limited to a few days, as longer use can result in rebound vasodilation.
  • Antigen-injection immunotherapy is very effective in treating inhalant allergies and can be considered in patients whose symptoms do not respond well to medications or in patients who cannot avoid the allergen in question (eg, cat owner allergic to cats). The mechanism of action of immunotherapy is not yet fully elucidated. Immunotherapy causes antigen-specific immunoglobulin G ₄ to be formed and lowers antigen-specific IgE over time. Some authorities theorize that immunotherapy results in an increase in the TH1-to-TH2 cell ratio.^{[31, 32]} Regulatory T cells may also play an important role.^[33]
  • An alternative to antigen-injection immunotherapy, aka, subcutaneous immunotherapy (SCIT), is sublingual/swallow immunotherapy (SLIT), which is currently being used with increasing frequency in Europe. It involves having the patient hold extract under the tongue for 1-3 minutes before swallowing. It offers the advantage of a lower likelihood of systemic adverse effects and has been shown to reduce allergic rhinitis and asthma symptoms. Studies thus far, however, indicate that SCIT may have a more significant impact on these symptoms than SLIT.^[31] SLIT is still being evaluated for FDA approval in the United States.
• Asthma

  • Avoid the offending allergen, if possible.
  • A key factor in controlling allergic asthma is controlling allergic rhinitis symptoms.
  • Therapy depends on the severity of disease.
    • Patients should have an albuterol metered-dose inhaler (MDI) (or nebulizers for young children) to use as needed.
    • Inhaled glucocorticosteroids should be added if appropriate. In general, these medications are used if symptoms occur more than twice weekly or if abnormal spirometry findings reverse with the inhalation of a short-acting bronchodilator. For more refractory symptoms, a long-acting beta agonist may be added to the inhaled glucocorticoid.
    • Leukotriene inhibitors can also be added.
    • Systemic corticosteroid bursts may need to be used for exacerbations of severe cases.
    • Patients with allergic asthma may respond well to specific allergen immunotherapy.
    • In patients refractory to the usual medications and who have antigen-specific IgE to perennial environmental aeroallergens (positive skin test or RAST result), therapy with omalizumab (Xolair), a humanized monoclonal antibody that prevents binding of IgE to high-affinity IgE receptors on mast cells and basophils, may result in improvement.^{[34, 35, 36]}
• Urticaria/angioedema

  • Avoid the offending allergen if known.
  • An H1-receptor blocker should be added. If symptoms are not controlled with this alone, an H2-receptor blocker, leukotriene inhibitor, or oral glucocorticosteroid can be added. Most patients require higher than the usual doses; employing twice daily H1 and H2 antihistamines for successful control is not uncommon.
• Atopic dermatitis

  • Avoid the offending allergen if possible, and properly hydrate and care for the skin.
  • Topical glucocorticosteroids and topical immunomodulators (eg, tacrolimus) can be used.^{[37, 38]}

• Consultation with an allergist, pulmonologist, and/or critical care medicine specialist may be necessary for protracted anaphylactic shock or severe asthma exacerbations.
• Consult an allergist or immunologist for the following conditions:

  • Allergic rhinitis not easily controlled with medications
  • Nonallergic, vasomotor rhinopathy
  • Asthma: Of patients with asthma, at least 50% of adults have allergies as factors causing or contributing to their asthmatic inflammation. More than 90% of children with asthma are allergic. Consider an allergy evaluation for seasonal bronchitis.
  • Allergy evaluation prior to the initiation of Xolair
  • Chronic urticaria or angioedema (>6 wk), or severe intermittent urticaria or angioedema, even if individual attacks last < 6 wk
  • History of anaphylaxis from insect bite or sting
  • History of anaphylaxis with unknown cause
  • Possible drug desensitization (if known allergy to drug for which no good alternatives are available)
  • Atopic dermatitis
  • Sinusitis before proceeding to surgery; nasal polyposis
  • Food allergy or idiosyncrasy
  • Persistent or bothersome conjunctivitis
  • Eosinophilic esophagitis or gastritis
  • Suspicion of congenital or acquired immune abnormalities
  • Diagnosis and treatment of acquired immunoglobulin deficiencies
  • Persistent pruritus

• Patients should avoid foods to which they are allergic.

  • Certain food proteins can cross-react with other proteins (eg, latex with avocado, banana, kiwi, chestnut, pineapple, passion fruit, apricot, and grape; ragweed with watermelon, cantaloupe, and honeydew melon; tree fruits with birch pollen).
  • Patients must be counseled about these possible cross-reactivities and should avoid the food if it causes symptoms.