When you are allergic to certain food, what food you eat or touch can affect your skin, but not all food-related skin reactions are triggered by allergy. For some people, certain foods can simply make an existing skin condition worse.

What is a food allergy?

For those people with a food allergy, eating a particular food can trigger an abnormal reaction in the body’s immune system. The immune system mistakes a protein in food for an "invader", and in attacking the invader it produces chemicals including histamine.This causes unpleasant symptoms, including ones that affect the skin, the digestive and the respiratory system.

The immune system can respond to a perceived "invader" in different ways. There could be an:

• IgE-mediated reaction. Antibodies called immunoglobulin E (IgE) release histamine. This reaction causes most allergy symptoms, including rashes, and they appear quickly, within seconds or minutes.

• Non-IgE mediated reaction. T cells (a type of white blood cell) cause symptoms such as rashes and eczema. These reactions are often less severe and take up to several hours to appear.

• Mixed IgE-mediated reaction and non-IgE mediated reaction. A mixture of the two reactions.

What skin-related symptoms can indicate a food allergy?

Symptoms of a food allergy or reaction that specifically affect the skin depend on how the immune system is responding.

If the response is IgE-mediated, symptoms include:

• Itching (pruritus)
• Redness of the skin (erythema)
• A raised itchy, red rash (urticaria or hives)
• Swelling of the skin (angioedema), usually in the lips, inside the mouth, the face and around the eyes

If the response is non-IgE-mediated, symptoms include:

• Itching (pruritus)
• Redness of the skin (erythema)
• Atopic eczema (atopic dermatitis) flares

As well as skin-related symptoms, a food allergy can also cause symptoms in the digestive tract and respiratory system, such as nausea, vomiting, abdominal pain, diarrhoea, blood or mucus in poo, constipation, sneezing, nasal congestion, cough, chest tightness, wheezing or shortness of breath. These may occur alone or along with skin reactions.

Although 5% of children and 3-4% of adults in the Western world have a food allergy, many more mistakenly believe they have a food allergy. However only 20% of people who believe they have an allergy have a true food allergy.

How is a diagnosis made?

If you or your child has skin symptoms such as a rash or eczema and you suspect it is linked to or made worse by something that is eaten, you should see your GP.

You will be asked questions about yourself and your family, including parents and siblings and questions about the symptoms, including how soon the symptoms appeared following contact with food, how long they lasted and how severe the symptoms were.

You may be asked to keep a diary to log what is eaten and any reactions so you might like to do this before going to the GP for the first time.

Detecting Food Allergies at Home

If you suspect you have food allergies or intolerances you can find out quickly and easily what foods your body can tolerate and which it cannot with the Cerascreen Food Reaction Test. The test can be carried out at home which may be less distressing, particularly for children, than a test at the doctor's surgery.

• Evaluates 56 foods using 40 parameters
• 95% of Europe's most important allergens are covered
• easy and convenient home sample-taking
• specialist diagnostic laboratory analysis
• identifies genuine allergies
• identifies likely intolerances