By Jointra Editorial Team, Certified EMT
Anaphylaxis is a severe, systemic allergic reaction that can cause death within minutes if untreated. It occurs when the immune system overreacts to an allergen — releasing massive amounts of histamine and other chemicals that cause blood vessels to dilate and airways to narrow simultaneously.
Anaphylaxis typically involves two or more body systems:
Skin: hives, flushing, itching, swelling (especially face, lips, tongue, throat)
Respiratory: wheezing, stridor, shortness of breath, throat tightness, hoarse voice
Cardiovascular: rapid or weak pulse, drop in blood pressure, dizziness, fainting
GI: nausea, vomiting, abdominal pain
Neurological: anxiety, sense of doom, confusion, loss of consciousness
The most dangerous signs are airway swelling and circulatory collapse. Either can be fatal without treatment.
Epinephrine (adrenaline) is the only first-line treatment for anaphylaxis. Antihistamines like diphenhydramine (Benadryl) do NOT treat anaphylaxis — they treat mild allergic reactions. Do not use them as a substitute.
Auto-injector use (EpiPen or generic): 1. Remove from carrier and take off safety cap 2. Hold with dominant hand, tip pointing down 3. Place against outer mid-thigh (can inject through clothing) 4. Push down firmly until you hear a click 5. Hold in place for 10 seconds 6. Remove and massage injection site for 10 seconds 7. Call 911 immediately
Epinephrine wears off in 15–20 minutes. Biphasic anaphylaxis — a second wave of reaction hours later — occurs in up to 20% of cases. The patient needs hospital observation even after symptoms resolve.
Call 911 immediately. Position the person lying flat with legs elevated (unless unconscious or having trouble breathing — then sit them up). There is no substitute for epinephrine.