Symptoms of Anaphylaxis

The time it takes the symptoms of anaphylaxis to develop depends on how the trigger entered the body.

If it was something the person ate, such as peanuts, then it can take anything from a few minutes to two hours.

If it was something that entered the skin, such as a sting or an injection, it will usually take 5-30 minutes. Symptoms can vary in severity.

Sometimes it can only cause mild itching or swelling, but in some people it can be extreme and lead to death.

Anaphylaxis is likely when all of the following 3 criteria are met

  • Sudden onset and rapid progression of symptoms
  • Life-threatening Airway and/or Breathing and/or Circulation problems
  • Skin and/or mucosal changes (flushing, urticarial (raised rash/welts etc), angioedema (swelling of eyes, lips, hands & feet).

The following supports the diagnosis

  • Exposure to a known allergen for the person.


  • Skin or mucosal changes alone are not a sign of an anaphylactic reaction
  • Skin and mucosal changes can be subtle or absent in up to 20% of reactions (some people can have only a decrease in blood pressure, i.e. a circulation problem)
  • There can also be gastrointestinal symptoms (e.g. vomiting, abdominal pain and incontinence).

Who is affected?

Anaphylaxis is uncommon. It is estimated that only 1 in 1,300 people in England will develop the symptoms of anaphylaxis at some point during their life.

Anaphylaxis affects people of all ages and is slightly more common in females than males.

People with other allergic conditions, such as asthma or the allergic skin condition atopic eczema, are most at risk of developing anaphylaxis.

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