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Diagnosing Food Allergies

Diagnosing food allergies requires a consultation with a skilled physician. Doctors or nurses who speak to those with a suspected food allergy needs to have the skills to ascertain important facts from the patient’s history. There are different types of allergic responses that can occur after exposure to things and while some of these can be tested for (with an IgE allergy blood test and allergy skin prick tests) other forms have no established diagnostic test.

An allergic reaction occurs when the immune system reacts in an inappropriate way to something which should be harmless. For those with an IgE mediated food allergy, the immune cell Immunoglobulin E will be raised against that food (otherwise known as allergen). On exposure to the triggering food, a rapid cascade of symptoms will occur such as hives (urticaria), swelling (angioedema), abdominal pain, vomiting, diarrhoea, runny nose or possible anaphylaxis. These reactions occur quickly after the exposure to the food that someone is allergic to and usually resolve within an hour or two. It is vital that a health professional recognises these types of food allergies as they can be life threatening.

Non IgE Mediated food allergies are harder to diagnose. Classically, families have many appointments with a doctor before the diagnosis is made and it is often an allergy expert who identifies the difficulties. These food allergies still involve the immune system reacting in an adverse way, but, the IgE will not be raised. These food allergies produce symptoms such as rashes, difficult to control eczema, reflux, abdominal pain, explosive nappies, blood in the stool, soft stool constipation, congestion, food aversion or failure to grow with impairment of height and/or weight. To diagnose these food allergies, the food needs to be removed from the diet for 2 to 4 weeks to see if there is treatment. If there is, the only way of being certain about the diagnosis is to rechallenge with the original food, to confirm that the symptoms of allergy return.

There are other rarer forms of food allergy such as FPIES (Food Protein Induced Enterocolitis Syndrome). Again, these types of food allergies cannot be tested for and rely on an allergy expert recognising the symptoms. FPIES causes profuse vomiting one to four hours after exposure to the food. It may take several allergic reactions before this allergy condition is recognised.

Eosinophilic Oesophagitis (EOE) is another type of allergic response which some people have. This occurs in adults and children and triggers symptoms such as indigestion, chest pains, food sticking on eating, regurgitation or vomiting. This condition is diagnosed by a gastroscopy/endoscopy. Biopsies need to be taken at multiple levels through the food pipe and allergy experts are looking to see if the eosinophils are raised in the cells. Again this form of allergy cannot be diagnosed by a blood test. There are a variety of ways of managing this condition including food restriction.

For many, food allergies are misdiagnosed or diagnosed late. If you are concerned that you or your child has food allergy and are looking to find the correct allergy diagnosis, please do contact us for support.

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