A food allergy occurs when the body's immune system mistakenly thinks proteins in food are a threat, and it launches an attack that we experience as unwanted symptoms. These vary depending on the food and the type of allergic response. Common foods to cause allergy include milk, eggs, peanuts, tree nuts, gluten or wheat, shellfish, white fish, soy, sesame and some fruit.
Common allergic responses come under gut problems, skin reactions and hay fever-like symptoms. Serious reactions include symptoms related to breathing or swelling around the face or mouth, and these require immediate medical attention.
If you have suspicions of a food allergy for you or your child, you may wish to have them tested. This can be done via your doctor, but the NHS often has strict criteria to warrant referral to the allergy service or for testing.
If you or your child don’t meet these criteria, but still wish to be tested, this can be arranged privately. Let’s take you through some of the tests and whether they are worthwhile or not. Unfortunately, any results require interpretation along with symptoms – they’re not black and white, you can’t say if an allergy is definitely present or absent. Keeping a food diary can be useful alongside any tests, and noting any patterns related to symptoms.
There are three types of food allergy, according to which part of the immune system is fighting them in the body:
· IgE-mediated food allergy, which is the most common, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms often occur a few seconds or minutes after eating and there's a greater risk of anaphylaxis.
· non-IgE-mediated food allergy, which is prompted by other cells in the immune system, not IgE antibodies. This takes several hours to develop after food has been eaten, so it's harder to relate the two and make a diagnosis.
· mixed IgE and non-IgE-mediated food allergies, where some people may experience symptoms from both types.
Allergy is one way we can react to certain foods. Other unwanted reactions come under the terms food sensitivity or food intolerance. These are not "true" allergies as they don't involve the immune system, but can cause discomfort and disruption to your health.
A quick response to suspected foods is more likely to be IgE-mediated. The best test for this is skin-pricking, where drops of certain food extracts are put on the forearm and a painless pin-prick exposes the immune system to each particular allergen. The reaction is documented by a specialist. If it becomes itchy, red and swollen around the area, this is considered a positive response.
This is usually done in a healthcare setting or clinic in the rare event of a serious reaction occurring.
A blood test can also be used to measure allergic antibodies in the blood.
A food elimination diet means that you avoid all food and related products of a suspected allergen from the diet for between two and six weeks, and see if symptoms improve. This test is complete if you then reintroduce it and symptoms return, giving you a positive result.
Food intolerance is entirely different to a food allergy – it's a different mechanism of response: it’s a difficulty digesting certain foods and therefore it will only cause gut problems without skin symptoms and without the risk of breathing problems and anaphylaxis. Sufferers often complain of bloating, excessive wind, diarrhoea, tummy pain and possible nausea and vomiting. Common intolerances include gluten (found in wheat and other grains) and lactose (found in milk and other dairy products). Food sensitivity is pretty much the same as intolerance.
The food elimination method is the most suitable test for suspected food intolerance or sensitivity.
If you have concerning symptoms, or you are worried about, for example, lactose intolerance in an infant, you should seek medical advice before withdrawing this food group and re-introducing it. Your infant or child has high nutritional needs, and therefore you should seek professional guidance to do this safely and meet their health needs to grow and thrive.
For mild symptoms in an adult, it may be reasonable to trial this yourself without advice, if you feel confident you can avoid all food products from a suspected food.
The best way to prevent an allergic reaction is to identify the food that causes the allergy and avoid it.
Histamines are often involved in an allergic response, so it’s a good idea to have antihistamines to hand. These are available at your pharmacy and can help relieve the symptoms of a mild or moderate allergic reaction. A higher dose of antihistamine is often needed to control acute or severe allergic symptoms, and your doctor will need to prescribe this.
People with a food allergy are often prescribed an adrenaline injection device such as EpiPen, which can be used as an effective treatment for more severe allergic symptoms in the case of emergencies.
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