What do food allergy rashes look like
Food allergies are divided into 3 types, depending on symptoms and when they occur.
- IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms occur a few seconds or minutes after eating.
There’s a greater risk of anaphylaxis with this type of allergy.
- non-IgE-mediated food allergy – these allergic reactions aren’t caused by immunoglobulin E, but by other cells in the immune system. This type of allergy is often hard to diagnose as symptoms take much longer to develop (up to several hours).
- mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types.
Read more information about the symptoms of a food allergy.
Oral allergy syndrome (pollen-food syndrome)
Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating unused fruit or vegetables.
This is known as oral allergy syndrome.
Oral allergy syndrome is caused by allergy antibodies mistaking certain proteins in unused fruits, nuts or vegetables for pollen.
Oral allergy syndrome generally doesn’t cause severe symptoms, and it’s possible to deactivate the allergens by thoroughly cooking any fruit and vegetables.
The Allergy UK website has more information.
The symptoms of a severe allergic reaction (anaphylaxis) can be sudden and get worse extremely quickly.
Initial symptoms of anaphylaxis are often the same as those listed above and can lead to:
- swollen tongue
- tight chest
- feeling dizzy or faint
- trouble swallowing or speaking
- breathing difficulties
Anaphylaxis is a medical emergency. Without quick treatment, it can be life threatening.
If you ponder you or someone you know is experiencing anaphylaxis, dial 999 and enquire for an ambulance as soon as possible.
Non-IgE-mediated food allergy
Another type of allergic reaction is a non-IgE-mediated food allergy. The symptoms of this type of allergy can take much longer to develop – sometimes up to several days.
Some symptoms of a non IgE-mediated food allergy 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 are sometimes thought of as being caused by something other than an allergy.
- vomiting with or without diarrhoea
- abdominal cramps
- in babies: excessive and inconsolable crying, even though the baby is well fed and doesn’t need a nappy change (colic).
What causes food allergies?
Food allergies happen when the immune system – the body’s defence against infection – mistakenly treats proteins found in food as a threat.
As a result, a number of chemicals are released. It’s these chemicals that cause the symptoms of an allergic reaction.
Almost any food can cause an allergic reaction, but there are certain foods that are responsible for most food allergies.
Foods that most commonly cause an allergic reaction are:
- tree nuts
- some fruit and vegetables
Most children that own a food allergy will own experienced eczema during infancy.
The worse the child’s eczema and the earlier it started, the more likely they are to own a food allergy.
It’s still unknown why people develop allergies to food, although they often own other allergic conditions, such as asthma, hay fever and eczema.
Read more information about the causes and risk factors for food allergies.
Some children can own a mixed reaction where they experience both IgE symptoms, such as swelling, and non-IgE symptoms, such as constipation.
This can happen to children who own 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, sometimes known as food-dependent exercise-induced anaphylaxis.
Drinking alcohol or taking an non-steroidal anti-inflammatory drug (NSAID) such as aspirin or ibuprofen may also trigger an allergy in people with this syndrome.
Sheet final reviewed: 15 April 2019
Next review due: 15 April 2022
A food allergy is when the body’s immune system reacts unusually to specific foods. Although allergic reactions are often mild, they can be extremely serious.
Symptoms of a food allergy can affect diverse areas of the body at the same time.
Some common symptoms include:
- an itchy sensation inside the mouth, throat or ears
- a raised itchy red rash (urticaria, or «hives»)
- swelling of the face, around the eyes, lips, tongue and roof of the mouth (angioedema)
Read more about the symptoms of food allergies.