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Symptoms - Food Allergy

The symptoms of a food allergy usually develop a few seconds or minutes after eating the food.

Some people may have a severe allergic reaction (anaphylaxis) which can be life threatening.

IgE-mediated food allergy

The most common type of allergic reaction to food is an IgE-mediated food allergy.

Symptoms include:

  • tingling or itching in the mouth
  • a raised, itchy red rash (hives) – in some cases, the skin can turn red and itchy, but without a raised rash
  • swelling of the face, mouth (angioedema), throat or other areas of the body
  • difficulty swallowing
  • wheezing or shortness of breath
  • feeling dizzy and lightheaded
  • feeling sick (nausea) or vomiting
  • abdominal pain or diarrhoea
  • hay fever-like symptoms, such as sneezing or itchy eyes (allergic conjunctivitis)


The symptoms of a severe allergic reaction (anaphylaxis) can be sudden and get worse quickly.

Initial symptoms of anaphylaxis are often the same as those listed above and can lead to:

  • swollen tongue
  • breathing difficulties
  • tight chest
  • trouble swallowing or speaking
  • feeling dizzy or faint
  • collapse

Anaphylaxis is a medical emergency. Without quick treatment, it can be life threatening.

Emergency action required: Call 112 or 999 and ask for an ambulance if:

  • you think you or someone you know is experiencing anaphylaxis

Non-IgE-mediated food allergy

The symptoms of this type of allergy can take much longer to develop - sometimes up to several days.

Symptoms may be what you would expect to see in an allergic reaction, such as:

  • redness and itchiness of the skin - although not a raised, itchy red rash (hives)
  • the skin becomes itchy, red, dry and cracked (atopic eczema)

Other symptoms can be much less obvious and may be caused by something other than an allergy.

They include:

  • vomiting with or without diarrhoea
  • abdominal cramps
  • constipation
  • excessive crying in babies, even though the baby is well fed and does not need a nappy change (colic).

Mixed reaction

Some children can have a mixed reaction where they experience both IgE symptoms and non-IgE symptoms. For example, they could have both swelling and constipation.

This can happen to children who have a milk allergy.

Exercise-induced food allergy

In some cases, a food allergy can be triggered after eating a certain food and then exercising. This can lead to anaphylaxis in severe cases.

Alcohol or non-steroidal anti-inflammatories (NSAIDs) may also trigger an allergy. For example, aspirin or ibuprofen.

Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 13 March 2021
Next review due: 13 March 2024