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Allergic Reactions — First Aid
What to do
- Stop the trigger if you can: remove the food from the mouth, brush off the insect or plant, rinse skin that contacted a chemical or cosmetic, and move away from the source.
- Watch the person closely for at least 30 minutes — allergic reactions can escalate. Know the anaphylaxis signs (see Anaphylaxis): difficulty breathing, swelling of tongue or throat, hoarse voice, dizziness or collapse.
- For mild skin reactions (itch, hives, mild swelling), a cool compress soothes itching. If the person has allergy medication prescribed for them (such as an antihistamine), help them take it as directed on their plan.
- If swelling involves the lips, tongue or throat, or breathing is affected in any way, treat it as anaphylaxis: call 911 and use an epinephrine auto-injector if available (see Anaphylaxis).
- Keep the person sitting comfortably (not lying flat if breathing is difficult) and do not leave them alone while symptoms evolve.
- Seek medical advice the same day even for mild reactions that settle, especially after a first reaction, so triggers and future plans can be discussed.
What NOT to do
- Do not assume a reaction will stay mild — anaphylaxis can develop from early mild signs.
- Do not give someone else's medication.
- Do not delay calling 911 if breathing, voice or circulation is affected — antihistamines do not treat anaphylaxis.
- Do not let the person drive themselves if they feel unwell or drowsy.
When to get medical care
Call 911 immediately for any reaction with breathing difficulty, throat or tongue swelling, hoarseness, persistent cough, dizziness, faintness, collapse, or widespread hives with feeling unwell — these are anaphylaxis until proven otherwise. Get same-day advice for eye or lip swelling, extensive hives, or any reaction in a baby.
Related conditions
Related procedures & tests
Related symptoms
Frequently asked questions
What is the difference between an allergy and anaphylaxis?
An allergy is the immune system's overreaction to a trigger; most reactions stay mild (itch, hives, sneezing). Anaphylaxis is a severe, whole-body reaction affecting breathing or circulation that can be fatal without epinephrine. Any breathing or circulation involvement means treat as anaphylaxis.
Can a mild reaction turn serious later?
Yes — symptoms can progress over minutes, and a second wave (biphasic reaction) can occur hours later, which is why hospital observation follows anaphylaxis and why escalating symptoms should never be watched at home alone.
In an emergency, call 911 (or your local emergency number) first — do not delay a call to read a guide. These pages are educational first-aid information in general terms; they are not a substitute for emergency services, first-aid training, or assessment by a qualified clinician.
