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What are the symptoms of a food allergy?

Certain food allergies cause immediate symptoms whereas in others it takes much longer for symptoms to develop.
The most common type of allergic reaction to food is known as an IgE-mediated food allergy.
In this type of allergy, the symptoms develop very quickly after eating the allergy-causing food (the allergen). Typically this can occur within a few minutes or in some cases, seconds.
Symptoms include:
  • Raised red itchy skin rash (urticaria), which can affect just one part of the body, or alternatively, spread across the whole body. In some cases, the skin can turn red and itchy but there is no raised rash
  • Swelling of the face, around the eyes, lips, tongue or the roof of the mouth
  • Feeling of narrowing in throat
  • Change in voice (croaky or hoarse) due to swelling in voicebox
  • Feeling dizzy and lightheaded
  • Feeling sick
  • Being sick
  • Abdominal pain and spasms
  • Diarrhoea
  • Cold-like symptoms, such as sneezing, runny nose and nasal congestion
  • Redness and irritation of the eyes (allergic conjunctivitis)
  • Coughing
  • Chest tightness
  • Wheezing or shortness of breath
In some cases, a severe food allergy (anaphylaxis) can be triggered after eating a certain food and then going on to exercise vigorously. This is known as food-dependent exercise-induced anaphylaxis.
A less common type of allergic reaction is known as non IgE-medicated food allergy. In this type of allergy, the symptoms take much longer to develop after eating the allergen; usually several hours or in some cases days.
Some symptoms will match what you would expect to see in an allergic reaction, such as:
  • Redness and itchiness of the skin (although not necessarily raised)
  • The skin becomes itchy, red, dry and cracked 
Some symptoms might not be as obvious and can easily be mistaken as something other than an allergy, such as:
  • Heartburn and indigestion that is caused by stomach acid leaking out of the stomach (gastro-oesophageal reflux disease)
  • Stools becoming much more frequent or loose (though it might not necessarily be considered as diarrhoea)
  • In babies: excessive and inconsolable crying even though the baby is well-fed and doesn't need a nappy change (colic)
  • Constipation
  • Redness around the anus, rectum and genitals
  • Unusually pale skin
  • Failure to grow at the expected rate
  • Mixed reaction
  • Some children can have a mixed reaction where they experience both "IgE" symptoms, such as swelling, and "non-IgE" symptoms such as constipation. This often happens to children who have a milk allergy.
Find out more about anaphylactic shock

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