Highlights of the New Guidelines for Severe Allergic Reaction

Approximately 2% to 5% of people experience a sudden, severe generalized allergic or hypersensitivity reaction (anaphylaxis) in their lifetimes, which potentially can be fatal if not treated promptly.

Medications, foods and stinging insects are the most common anaphylaxis triggers (allergens). The risk factors for severe anaphylaxis are old age and having a chronic condition, such as asthma or heart or blood vessel disease.

A workgroup of volunteer experts from the American Academy of Allergy, Asthma & Immunology and the American College of Allergy, Asthma, and Immunology reviewed the evidence from 32 relevant clinical studies and provided updated guidelines for assessing and managing anaphylaxis.

The new guidelines were published in the April 2020 issue of the Journal of Allergy and Clinical Immunology.

Key points of the new guidelines[1]

The workgroup embraced three previously validated criteria, any one of which makes it highly likely that a person is experiencing anaphylaxis based on specific signs and symptoms for cases that involve exposure to a likely allergen for that person or those that do not involve exposure to a known allergen (see Text Box below).

The workgroup emphasized that the prompt and — if needed — repeated injection every five to 15 minutes of epinephrine (ADRENACLICK, ADRENALIN, AUVI-Q, EPIPEN, EPIPEN JR, SYMJEPI) into the muscle of the outer thigh is the only treatment of choice for anaphylaxis. This is because epinephrine works within minutes to treat, reverse and prevent the escalation of all symptoms associated with such allergic reaction and can be lifesaving.

The guidelines indicated that up to 20% of patients experience biphasic reactions (repeated anaphylaxis occurring within one to 72 hours after resolution of an initial anaphylactic episode). Patients with severe anaphylaxis, those who require multiple doses of epinephrine and those with delayed administration of epinephrine are at greatest risk of biphasic reactions. Therefore, the guidelines recommend observing patients with mild episodes for an hour after resolution of symptoms and observing those with severe symptoms for at least six hours after an initial anaphylaxis episode. The guidelines also recommend epinephrine as the treatment of choice for such biphasic reactions.

The guidelines do not recommend the routine use of antihistamines, such as diphenhydramine (BENADRYL), or glucocorticoids, such as hydrocortisone (CORTEF), to treat severe anaphylaxis symptoms or to prevent biphasic reactions. However, they indicate that antihistamines can be given after epinephrine to reduce acute skin reactions, such as itching and urticaria.

Finally, the guidelines do not recommend the use of antihistamines and corticosteroids to prevent reactions to radiocontrast agents (used for medical imaging) in patients with prior hypersensitivity to such substances. However, they do not rule out the use of these medications to prevent reactions before treatment with certain chemotherapy or immunotherapy medications.

Criteria Making the Diagnosis of Anaphylaxis Highly Likely

A person is highly likely to be experiencing anaphylaxis when any of the following three sets of circumstances occurs:

• Sudden onset of an illness (within minutes to several hours) involving skin or mucous membrane signs and symptoms (for example, generalized hives, itching or flushing, or swollen lips or tongue) and at least one of the following: (a) sudden respiratory signs or symptoms (forexample, cough, shortness of breath or wheezing) or (b) sudden drop inblood pressure or symptoms of major organ dysfunction (for example, generalized decreased muscle tone [collapse] or incontinence);
• At least two of the following occur suddenly within minutes to hours of exposure to a known allergen for the person: (a) skin or mucous membranesigns and symptoms, (b) respiratory signs and symptoms, (c) drop in blood pressure or symptoms of major dysfunction, or (d) gastrointestinal symptoms(for example, crampy abdominal pain or vomiting); or
• A drop in blood pressure (less than 90 systolic blood pressure orgreater than 30% decrease in diastolic blood pressure in adults) within minutes to hours of exposure to a known allergen for the person.

What You Can Do

If you think you are experiencing an anaphylaxis reaction and have access to an epinephrine autoinjector, inject it into your upper thigh muscle right away, then seek emergency medical help. If you do not have access to epinephrine, seek emergency medical help right away. You should remain under medical observation until your symptoms have fully resolved and for an appropriate time thereafter to monitor for possible biphasic reactions.

See an allergist for further evaluation and management and to learn about the appropriate use of epinephrine auto-injectors, as applicable. Do your best to completely avoid your allergic triggers, as even small exposures to any of them can cause a severe allergic reaction.

If you or a family member has experienced an anaphylaxis reaction in the past, you should always carry an epinephrine autoinjector, or two if you experienced severe or biphasic anaphylaxis in the past.
 

References

[1] Shaker MS, Wallace DV, Golden DBK, et al. Anaphylaxis—a 2020 practice parameter update, systematic review, and grading of recommendations, assessment, development and evaluation (GRADE) analysis. J Allergy Clin Immunol. 2020;145(4):1082-1123.