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