Food allergy testing in children with eczema: is it useful?

In the UK, around one in five children have eczema. Even though they are separate conditions, children with eczema quite often develop food allergies, especially if the symptoms of their skin condition are severe.

Some children benefit from food allergy testing or removing certain foods from their diet, but this is not usually necessary in those with mild symptoms of eczema and no issues with foods. Many parents, however, try excluding foods from their child’s diet without seeking professional advice, to see whether this helps their child’s eczema. We spoke to one of London’s leading paediatric allergists Dr Robert Boyle about the links between eczema and food allergies and what he suggests parents should do.

Are children with eczema likely to have allergies?

In some cases, the symptoms of eczema will largely disappear before a child starts primary school, without long term consequences. For other children, however, eczema can be a persistent and troublesome condition for many years.

Eczema can be the first sign of a genetic tendency to develop allergic conditions such as hay fever or asthma. We know that children whose eczema starts in the first months of life are more prone to developing food allergies than children without eczema.

How can a doctor diagnose a food allergy in my child?

Often, parents will make the allergy diagnosis themselves, for example, if there is a sudden onset of vomiting and diarrhoea or rash after their little one eats scrambled eggs.

Doctors can confirm the cause of these immediate reactions by offering an allergy blood test or skin prick test. But even in the absence of such obvious physical reactions, parents often question whether a food allergy is contributing to their child’s eczema, or if their child is likely to have an allergic reaction to new food in the future. An allergy test can help to find that out, by identifying foods which might be contributing to a child’s eczema, or foods which they are likely to have an allergic reaction to in the future
 

Are food allergy tests valuable in cases of eczema?

It can be difficult to link any given food to a worsening of eczema because eczema can flare for other reasons and symptoms triggered by foods may not appear for hours or occasionally days after the food has been eaten.

The value of allergy tests in these circumstances is uncertain as we don’t really know how commonly food allergy worsens eczema symptoms. Although eczema and food allergy often occur together, food allergy is not the main cause of eczema. Many experts believe that it is eczema which leads to the development of allergy to foods.

Another uncertainty about the value of allergy tests in children with eczema is that tests can be ‘false positive’. So a child who tests positive may be ‘sensitised’ to food as opposed to ‘allergic’. This means that they can actually eat that food without any apparent ill-effect. Testing could potentially lead to unnecessary and unhelpful dietary restrictions.
 

What about investigating food allergies in older children or those with mild eczema?

For children with early-onset, difficult to treat eczema, your GP may refer your child for food allergy tests or may advise trying an exclusion diet. However, anti-inflammatory creams or ointments are the most effective way to treat eczema, and troublesome eczema often just needs more anti-inflammatory treatment to be applied for a longer period of time to calm it down.

Investigating for the possibility of food allergies in older children or those with mild eczema symptoms is less common. Parents or doctors may not have any concerns about food allergy and the likelihood of food allergy is not very different from children with no eczema.

Care needs to be taken with exclusion diets, especially those which are hard to avoid like dairy products or wheat. These diets can be quite a burden for child and family. Although many more free-from products are now available, severe dietary restrictions without appropriate supervision can lead to nutritional deficiencies.
 

What research is currently being carried out?

With colleagues at the University of Nottingham and University of Oslo, we are exploring the possibility that eczema can be prevented using moisturisers, and that this might, in turn, reduce risk of food allergy developing.

With colleagues at the Universities of Bristol, Southampton and Nottingham, we have just completed a trial exploring whether there might be a role for routine allergy history and skin prick testing to guide diet in young children with eczema.
 

What can parents and clinicians do?

The best advice is to use two simple treatments, emollients and topical corticosteroids, to control eczema symptoms if they are severe enough to trouble your child. If there are any immediate food reactions or despite good skincare, your child’s skin is causing misery, parents should seek further help from their family doctor regarding the possibility of food allergy.

Dr Boyle is an expert in treating asthma, allergic reactions, anaphylaxis and food intolerance and allergies in children. You can book an appointment for your child to see him via his Top Doctor’s profile.