Anaphylaxis Symptoms and What to Do

What anaphylaxis looks like

Anaphylaxis is likely when symptoms start suddenly after a possible trigger and affect more than one part of the body. Doctors look for at least two of these groups, or for low blood pressure alone after a known allergen:

Skin and mouth (in about 80 to 90% of cases)

• hives: raised, itchy welts anywhere on the body
• flushing or redness, often of the face and chest
• itching, especially of the palms, soles, scalp or mouth
• swelling of the lips, tongue, eyelids or face (angioedema)

Airway and breathing

• throat swelling, tightness or a feeling of the throat closing
• hoarse voice, difficulty swallowing, drooling
• wheezing, coughing, chest tightness
• shortness of breath or noisy breathing (stridor)
• runny nose and sneezing

Heart and circulation

• dizziness, lightheadedness or fainting
• a fast, weak pulse, which can progress to shock
• pale, cold, clammy skin, or blue lips
• low blood pressure and collapse (anaphylactic shock)

Gut

• nausea and vomiting
• cramping belly pain
• diarrhea

Other

• a sense of impending doom, anxiety
• metallic taste
• in women, uterine cramps

Early signs of anaphylaxis

The first symptoms are often subtle:

• tingling or itching of the lips, mouth or throat
• a warm, flushed feeling
• sudden sneezing, nasal congestion or watery eyes
• a sudden feeling of unease or "something is wrong"
• a few hives or itchy skin

These can progress to breathing or circulation problems in minutes. If someone with a known severe allergy has these after exposure, many allergy action plans advise giving epinephrine immediately.

How quickly anaphylaxis starts

The faster it starts, the more severe it tends to be. About 1 in 20 people have a second wave of symptoms (a biphasic reaction), usually within 12 hours, without further exposure.

Anaphylaxis symptoms in children and babies

Children often have the same signs as adults, but may describe them differently: "my tongue feels hot", "there's something stuck in my throat", "my mouth feels funny". Babies and toddlers may show:

• sudden crying or irritability
• vomiting, often repeated, after a new food
• hives around the mouth or across the body
• coughing, hoarse cry or noisy breathing
• sudden sleepiness or floppiness, which is a sign of low blood pressure

Food allergy, especially to peanut, tree nuts, milk, egg, sesame and fish, causes most anaphylaxis in children.

What to do: anaphylaxis first aid

1. Give epinephrine (adrenaline) straight away. Use the person's auto-injector or nasal spray, into the outer thigh, through clothing if needed. Hold an auto-injector in place for the time on the label.
2. Call 911 or your local emergency number and say "anaphylaxis".
3. Position the person: lying flat with legs raised if they are dizzy or faint. Sitting up if they are struggling to breathe. On their side if vomiting or unconscious. Do not let them stand or walk, even if they feel better, because sudden collapse can follow.
4. Give a second dose after 5 to 15 minutes if symptoms are not improving or get worse, and a second device is available.
5. Start CPR if they stop breathing normally.
6. Remove the trigger if still present, such as a bee sting (scrape it out) or an IV drip.

Antihistamines and asthma inhalers can be given after epinephrine for hives and wheeze, but they do not treat anaphylaxis and must never delay epinephrine.

Everyone treated with epinephrine for anaphylaxis should be checked in an emergency department, even if they recover fully.

Anaphylaxis vs other reactions

When unsure, treat as anaphylaxis. Epinephrine is safe for most people and delay is the main cause of death.

Who is at higher risk of severe symptoms

• people with asthma, especially if poorly controlled
• teenagers and young adults with food allergy, who are more likely to delay treatment
• older adults and people with heart disease
• people taking beta blockers, which can make epinephrine less effective
• people with mastocytosis
• exercise, alcohol, NSAIDs and infections can make a reaction worse

After a reaction

Ask for a referral to an allergist to confirm the trigger, get a written anaphylaxis action plan, and get a prescription for two epinephrine auto-injectors to carry at all times. The anaphylaxis condition page covers triggers, testing, emergency treatment and long-term prevention in detail.

Frequently asked questions

What are the first signs of anaphylaxis?

Early signs often include tingling or itching in the mouth, flushing, hives, sneezing and a sudden sense that something is wrong. Within minutes these can progress to throat tightness, wheezing, vomiting, dizziness or collapse. If you have a known severe allergy, treat early with epinephrine.

How fast do anaphylaxis symptoms start?

Usually within 5 to 30 minutes of exposure. Reactions to injected medicines and stings can start within seconds to minutes. Food reactions can take up to 2 hours, and alpha-gal red meat allergy can take 3 to 6 hours. Symptoms can also return hours later.

Can you have anaphylaxis without hives?

Yes. Up to about 1 in 10 people have no skin symptoms, particularly when blood pressure drops rapidly. Breathing difficulty, faintness or collapse after a likely trigger should be treated as anaphylaxis even without hives or swelling.

Should I use an EpiPen if I am not sure it is anaphylaxis?

Yes, if you have been prescribed one and have symptoms after a likely trigger. Guidelines advise using epinephrine when in doubt, because delay increases the risk of death, while epinephrine is safe for most people. Then call 911.

Do I need to go to the hospital if the EpiPen worked?

Yes. Epinephrine wears off in 10 to 20 minutes and symptoms can return, sometimes hours later. You need monitoring, possibly more treatment, and advice on follow-up. Call 911 rather than driving yourself.