Food allergy tests

There are three types of food allergies, according to which part of the immune system is fighting them in the body:

• IgE-mediated food allergy, which is the most common, is 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. It takes several hours to develop after eating food, 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. This is considered a positive response if it becomes itchy, red, and swollen around the area.

This is usually done in a healthcare setting or clinic in the rare event of a severe reaction occurring.

A blood test can also be used to measure allergic antibodies in the blood.

A food-elimination diet means avoiding all food and related products of a suspected allergen from the diet for two to six weeks and seeing if symptoms improve. This test is complete if you reintroduce it and symptoms return, giving you a positive result.

Food intolerance is entirely different from a food allergy – it's a different mechanism of response: it's a difficulty in 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 gas, diarrhea, tummy pain, and possibly 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.

Suppose you have concerning symptoms, or you are worried about, for example, lactose intolerance in an infant. In that case, 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 on 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 epinephrine injection device such as EpiPen, which can be used as an effective treatment for more severe allergic symptoms in the case of emergencies.