Anaphylaxis Recognition

Why this matters

Anaphylaxis kills in two ways. Swelling can close the airway. Blood vessels can open wide until the blood pressure falls. That vessel problem is distributive shock. Give IM epinephrine first. Do not wait for hives or one more symptom. Some patients have gut pain, vomiting, and low blood pressure after a known allergen, with no rash. That is still anaphylaxis.

Working Field Picture

• It starts suddenly after an exposure such as food, a sting, a drug, or latex. Sometimes nobody knows the exposure.
• Skin and mouth findings include hives, flushing, and swelling. They help, but they are not required.
• Breathing findings include wheeze, stridor, shortness of breath, and a low sat. Stridor is a high-pitched sound from a swollen upper airway.
• Circulation findings include low blood pressure, fainting, and collapse.
• Gut findings can include cramps, vomiting, and diarrhea.

Clinical sequence

1. Give IM epinephrine as soon as the picture fits. Use the mid-anterolateral thigh, the outer front of the thigh. Do not wait for an IV, a full-body rash, or an antihistamine.
2. Give high-flow oxygen. If the blood pressure is low, lay them flat with the legs raised unless airway swelling or vomiting makes that unsafe. Be ready for a difficult airway.
3. Remove the ongoing exposure if you can do it safely. A stinger still in the skin is one example.
4. Give IV fluid for low blood pressure per protocol. Use second-line drugs only if you are authorized.
5. Antihistamines and steroids may be add-on drugs in your protocol. They do not replace epinephrine. Do not give them first.
6. Reassess. Symptoms can return after the patient looked better. That return is a biphasic reaction. Transport and keep watching.

Key points

• Epinephrine is the first drug. If asthma and anaphylaxis are both present, give IM epinephrine first, then a bronchodilator. That order is the GINA 2026 teaching.
• Anaphylaxis can be present with no rash. Do not wait for one.
• Patients on beta-blockers can be harder to resuscitate. Still follow your protocol.
• Write down the exposure, the time of each epinephrine dose, the response, and the airway status.

Common errors

• Giving only diphenhydramine when more than one body system is involved and the patient is in shock.
• Delaying IM epinephrine so you can start an IV.
• Calling it anxiety when the patient has low oxygen and low blood pressure after peanuts.

Practice

Related: Epinephrine lesson, Shock categories.

Sources & Further Study

Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.

• NASEMSO National Model EMS Clinical Guidelines (2022) — U.S. EMS model language; your protocol still decides care
• AAAAI/ACAAI Anaphylaxis Practice Parameter (2023 update)
• IM epinephrine in the mid-anterolateral thigh is first-line. Do not delay for IV access, rash, or antihistamines.
• GINA 2026 Strategy Report — if anaphylaxis and asthma present together, epinephrine first, then bronchodilators
• Your allergic reaction / anaphylaxis protocol.