Anaphylaxis
Epinephrine First. Do Not Wait
General information from an emergency physician. It adds to your discharge papers and does not replace them or your own doctor. What this site is and isn’t
Key Takeaways:
- Epinephrine is the first treatment for anaphylaxis. Antihistamines do not replace it.
- A second wave can occur without another exposure.
- Fill, carry, and practice with the prescribed auto-injectors.
About Your Diagnosis & ED Workup
Anaphylaxis is a fast whole-body allergic reaction. Chemicals released by immune cells can swell the airway, tighten breathing tubes, and make blood pressure fall.
Skin symptoms are common but are not required. Breathing trouble, low blood pressure, or symptoms in several body systems after an exposure can meet anaphylaxis criteria.
First Steps & Evidence-Based Home Care
Fill the epinephrine auto-injector prescription and carry both devices. Ask a pharmacist or clinician to watch you use a trainer device. Technique fades without practice.
Use epinephrine first at the first sign of anaphylaxis. Antihistamines may help itching and hives, but they do not treat airway swelling or shock.
If symptoms remain or return 5 to 15 minutes after the first dose, use the second prescribed dose and return to the emergency department.
Timeline & Expected Recovery Course
Symptoms can return without a new exposure, usually 1 to 48 hours after the first reaction ends.
The largest registry found a second wave in 4.7% of cases. Risk is higher after a severe first reaction or more than one epinephrine dose.
Emergency Red Flags (When to Return Immediately)
Use prescribed epinephrine and return to the emergency department for any of these. This list is not exhaustive.
- Throat tightness, hoarseness, noisy breathing, wheezing, or trouble breathing, because anaphylaxis can quickly narrow the airway and breathing tubes.
- Swelling of the lips, tongue, or throat, because swelling can spread into the airway.
- Repeated vomiting with dizziness, faintness, or a sense of doom, because symptoms in several body systems can signal anaphylaxis and falling blood pressure.
- Any return or worsening after improvement, because a second reaction can occur without another exposure.
Reviewed September 3, 2026