01 — Recognizing anaphylaxis
Anaphylaxis involves two or more body systems at once. That is the key distinction from a mild allergic reaction.
The AHA and Red Cross 2024 First Aid Guidelines define anaphylaxis as a life-threatening, systemic allergic reaction. What separates it from a simple allergic reaction is that it involves multiple body systems simultaneously. A person with hives alone has an allergic reaction. A person with hives plus throat tightness, or skin symptoms plus a drop in blood pressure, is showing signs of anaphylaxis.
Common triggers include foods (peanuts, tree nuts, shellfish, milk, eggs, soy, wheat), medications (penicillin, sulfa drugs), insect venom (bee, wasp, hornet stings), animal dander, and latex. Anaphylaxis can begin within seconds to minutes of exposure.
Skin
- Hives or rash
- Facial or lip swelling
- Flushing or pallor
- Itching
Respiratory
- Sensation of throat closing
- Difficulty breathing
- Wheezing or coughing
- Hoarse voice
Cardiovascular
- Dizziness or fainting
- Rapid or weak pulse
- Pallor (pale skin)
- Low blood pressure
Gastrointestinal
- Nausea or vomiting
- Abdominal cramps
- Diarrhea
Changes in mental status, sudden confusion, or a sharp drop in alertness in the context of a known allergen exposure are also warning signs. Anaphylaxis can progress to unconsciousness and cardiac arrest without rapid treatment.
02 — Epinephrine
Epinephrine first. Always. Antihistamines and inhalers do not treat anaphylaxis.
Common mistake
Give an antihistamine (like Benadryl) first to see if it helps before using the epinephrine auto-injector.
AHA / AAP guidance
Antihistamines treat itching and hives, but they do not relieve throat closing, breathing difficulty, low blood pressure, or shock. They are not appropriate as the initial treatment or the only treatment for anaphylaxis. Delayed epinephrine is associated with worse outcomes and increased risk of death. Use epinephrine immediately.
Epinephrine is the only drug that rapidly reverses the multiple system effects of anaphylaxis. It works within minutes to open airways, restore blood pressure, and reduce swelling. The AHA 2024 guidelines state that first aid providers may assist a person experiencing anaphylaxis to self-administer their prescribed epinephrine auto-injector if the person is unable to do so due to respiratory distress, altered mental status, or hypotension.
The injection site specified in both the AHA 2024 guidelines and the Red Cross training materials is the outer middle of one thigh. The lateral thigh provides consistent intramuscular absorption and is accessible even through light clothing. The auto-injector is held at a 90-degree angle to the thigh, pressed firmly until a click is heard, and held in place for 3 seconds. The injection area is then massaged for 10 seconds.
Always call 911 before or immediately after administering epinephrine. Epinephrine may improve symptoms temporarily, but its effects can wear off. The person needs emergency medical evaluation. If symptoms return or worsen 5 to 10 minutes after the first dose and emergency services have not yet arrived, a second dose may be given if available.
03 — Asthma attack response
Help them use their prescribed inhaler. Position matters. Call 911 if the inhaler does not work.
The AHA 2024 First Aid Guidelines specify that it is reasonable for first aid providers to assist a person with a diagnosed asthma attack to use their prescribed inhaled bronchodilator (such as albuterol) when they are having difficulty breathing. The person should be sitting upright in a position they find comfortable for breathing. Do not lay them down.
A standard puffer inhaler delivers medication most effectively when the person exhales fully before inhaling the dose slowly and deeply, then holds their breath for about 10 seconds before exhaling. If the person has a spacer device available, use it. A spacer increases the amount of medication that reaches the lungs rather than depositing in the mouth or throat.
When to call 911 for asthma
Call 911 if the inhaler does not provide relief within a few minutes, if the person cannot complete a sentence, if their lips or fingernails are turning blue, if they are breathing very rapidly with visible effort, or if they become confused or lose consciousness. These are signs the airway obstruction is severe.
Note that an asthma inhaler is not a substitute for epinephrine in anaphylaxis. If a person with known allergies and asthma develops anaphylaxis, the epinephrine auto-injector is the priority treatment. An inhaled bronchodilator may help with lower respiratory symptoms as a secondary measure, but it will not reverse the cardiovascular and systemic effects of anaphylaxis.
Quick reference
- Anaphylaxis = allergic reaction involving two or more body systems at once; it is life-threatening
- Key distinguishing signs: throat tightness or difficulty breathing combined with skin reaction, or skin reaction combined with dizziness or blood pressure drop
- Epinephrine first, always — antihistamines treat itching and hives but do not reverse airway closure, low blood pressure, or shock
- Injection site: outer middle of the thigh (lateral thigh), at 90 degrees, hold 3 seconds after click, massage 10 seconds
- Call 911 immediately — epinephrine effects can wear off; the person needs emergency evaluation
- Second dose may be given 5 to 10 minutes after the first if symptoms persist or return and EMS has not arrived
- Asthma attack: sit upright, assist with prescribed inhaler, use spacer if available; call 911 if inhaler does not work within a few minutes
- An asthma inhaler is not a substitute for epinephrine in anaphylaxis
Primary sources
- AHA / Red Cross — 2024 First Aid Guidelines: Anaphylaxis signs and symptoms involve multiple body systems; epinephrine typically injected into the lateral thigh; first aid providers may assist self-administration; first aid providers should help with inhaled bronchodilators for diagnosed asthma.
- Red Cross — Allergic Reaction / Anaphylaxis: Injection into outer middle of thigh at 90 degrees; hold 3 seconds after click; massage 10 seconds; second dose after 5 to 10 minutes if symptoms persist and EMS has not arrived; call 911 immediately.
- AAP — Epinephrine for First-Aid Management of Anaphylaxis (reaffirmed 2024): H1-antihistamines treat itching and hives but do not relieve life-threatening respiratory symptoms, hypotension, or shock; they are not appropriate as the initial or only treatment; delayed epinephrine is associated with increased hospitalization and mortality.