Allergic reactions range from mild localized symptoms to life-threatening anaphylaxis. Recognizing the signs early and knowing how to administer epinephrine is essential for anyone who cares for a person with known allergies.

First aid kit with epinephrine auto-injector for allergies — Anaphylaxis is a severe, life-threatening allergic reaction requiring immediate epinephrine administration. Allergies affect millions worldwide with increasing prevalence. Source: Unsplash.

Mild to Moderate Allergic Reactions

Symptoms of mild allergic reaction include: hives (urticaria) — raised, itchy red welts on the skin; itching (pruritus) localized to the area of contact; nasal congestion, sneezing, runny nose; watery, itchy eyes (allergic conjunctivitis); and localized swelling (angioedema) around the eyes, lips, or contact site.

Treatment for mild reactions: remove the trigger if possible (wash skin, rinse mouth, remove stinger). Administer oral antihistamines (diphenhydramine/Benadryl, cetirizine/Zyrtec, loratadine/Claritin). Apply cool compresses to hives. Monitor for progression of symptoms — mild reactions can escalate to anaphylaxis rapidly.

Patient Perspective

As a patient with allergies, you should carry antihistamines at all times, wear a medical alert bracelet listing your allergies, have an action plan developed with your allergist, and teach family, friends, and coworkers to recognize anaphylaxis and use your epinephrine auto-injector.

Ambulance for anaphylaxis emergency transport — Emergency medical services transport patients with severe allergic reactions for hospital evaluation and monitoring. Source: Unsplash.

Anaphylaxis — Recognition

Anaphylaxis is a severe, life-threatening allergic reaction that occurs rapidly after exposure to an allergen. It affects multiple body systems simultaneously.

Skin and mucous membranes. Hives, itching, flushing, swollen lips/tongue/uvula, periorbital edema (swelling around the eyes).

Respiratory system. Difficulty breathing, wheezing, stridor (high-pitched breathing sound from upper airway), shortness of breath, chest tightness, throat tightness, hoarseness, sensation of throat closing.

Cardiovascular system. Hypotension (low blood pressure), dizziness, fainting, pallor, weak or rapid pulse, cyanosis.

Gastrointestinal system. Nausea, vomiting, abdominal cramps, diarrhea (may be bloody).

Neurologic. Sense of impending doom, anxiety, confusion, loss of consciousness.

Danger Signs

The most dangerous signs of anaphylaxis are: difficulty breathing or stridor, swelling of the tongue or throat, hoarseness or difficulty speaking, hypotension or dizziness, collapse or loss of consciousness, and rapid progression of symptoms. ANY combination of symptoms affecting two or more body systems after allergen exposure should be treated as anaphylaxis.

Common Triggers

Food allergens. Peanuts, tree nuts (walnuts, almonds, cashews), shellfish (shrimp, crab, lobster), fish, milk, eggs, wheat, soy, and sesame. These account for most food-induced anaphylaxis in the United States. Peanut and tree nut allergies tend to be lifelong and carry the highest risk of severe reactions.

Insect stings. Hymenoptera venoms from bees, wasps, hornets, yellow jackets, and fire ants. Stings can cause anaphylaxis even in people without a history of allergic reactions to stings.

Medications. Penicillin and other beta-lactam antibiotics are the most common cause of drug-induced anaphylaxis. NSAIDs (aspirin, ibuprofen, naproxen), ACE inhibitors, radiocontrast media, and chemotherapeutic agents can also trigger anaphylaxis.

Latex. Natural rubber latex found in gloves, catheters, and medical equipment. Cross-reactivity with certain fruits (banana, avocado, kiwi, chestnut) is common.

Exercise-induced anaphylaxis. Occurs during or after exercise, often in association with eating a specific food (wheat, shellfish, celery) within a few hours before exercise.

⚠ Clinical Correlation

Up to 20% of anaphylaxis cases involve a biphasic reaction — symptoms recur 1 to 8 hours (sometimes up to 72 hours) after the initial reaction resolves, despite treatment. The second phase can be as severe as or worse than the first. For this reason, patients who receive epinephrine for anaphylaxis should be transported to the emergency department and observed for at least 4-6 hours (longer if the initial reaction was severe). Steroids are sometimes given to reduce the risk of biphasic reactions, though evidence is mixed. Discharge instructions should include a plan for return if symptoms recur.

Epinephrine Auto-Injector Administration

Steps for Using an EpiPen (Auto-Injector)

Activate EMS. Call 911 before or immediately after administering epinephrine, depending on the situation. This is the first step.
Remove the safety cap from the auto-injector (blue cap on EpiPen, green or red cap on generics).
Position the orange (needle) end against the outer mid-thigh. Can be administered through clothing if necessary.
Swing and jab firmly into the thigh until you hear a click. Hold in place for 3 seconds (or count to 3).
Remove the injector and massage the injection site for 10 seconds to help absorption.
Note the time of administration.
Call 911 if you have not already. Say “Anaphylaxis, epinephrine administered.”
Prepare for a second dose. If symptoms do not improve in 5-15 minutes and 911 has not arrived, a second dose can be administered in the opposite thigh (if you have a second auto-injector).

Important Points

Epinephrine is the first-line treatment for anaphylaxis. There are no absolute contraindications when anaphylaxis is suspected. Delayed administration of epinephrine is the leading cause of death in anaphylaxis. Antihistamines are not a substitute for epinephrine in anaphylaxis — they work too slowly and do not address airway obstruction or hypotension. The auto-injector should be stored at room temperature (59-86°F) away from extreme heat or cold. Check expiration dates regularly.

⚠ Caution

When anaphylaxis is suspected, do not wait for severe symptoms to develop before administering epinephrine. Early administration is safer and more effective. The risk of death from anaphylaxis far outweighs the risk of transient side effects from epinephrine (pallor, tremors, palpitations, anxiety, headache). These side effects are temporary and resolve as the epinephrine is metabolized. Epinephrine does not cause serious harm if given unnecessarily in the setting of a suspected allergic reaction — it is far better to give epinephrine and be wrong than to delay and lose the patient.

Emergency Action Plan

Every person with a known severe allergy should have a written anaphylaxis emergency action plan. The plan includes:

List of allergens (triggers) for the patient
Signs and symptoms of mild vs. severe reactions
When to use antihistamines vs. epinephrine
Step-by-step instructions for epinephrine administration
Follow-up steps (go to emergency department, even if symptoms resolve)
Emergency contact numbers (parent, guardian, allergist, primary care)
Current photo of the patient (for school or daycare)

Follow-Up Care

After successful emergency treatment: the patient must be transported to the emergency department for evaluation and observation (due to biphasic reaction risk). Blood tests (tryptase levels) can confirm anaphylaxis. The patient should have a follow-up appointment with an allergist or immunologist for allergen testing and long-term management. Prescriptions for additional auto-injectors and an updated action plan should be provided. Referral to a support group or counseling may be helpful for patients with significant anxiety about future reactions.

Prevention Strategies

Strict avoidance of known triggers
Reading food labels carefully (Food Allergy Labeling and Consumer Protection Act — FALCPA requires labeling of major allergens)
Informing restaurants and food service staff about allergies
Carrying epinephrine auto-injectors at all times (two doses)
Wearing a medical alert bracelet or necklace
Developing a written emergency action plan
Educating family, friends, coworkers, and school staff
Periodic follow-up with an allergist to reassess allergy status (some allergies, especially food allergies in children, may resolve)

Summary

Mild allergic reactions are treated with antihistamines and trigger removal. Anaphylaxis requires immediate epinephrine administration followed by EMS transport to an emergency department. The key factors in anaphylaxis survival are early recognition, rapid epinephrine use, EMS activation, and observation for biphasic reactions. Prevention through trigger avoidance and having an action plan is essential. Antihistamines are not a substitute for epinephrine in severe reactions.