Is food allergy the cause of eczema?
No. Children are born with the tendency to have eczema and many things can make this eczema worse. A “trigger” is anything that makes it worse. Foods can be a trigger for eczema, but they are not the cause. One way to think of it is that eczema results from an imbalance of the immune system. As a result of this imbalance a child may become sensitive (develop IgE allergy antibodies) to common things in the environment (e.g. foods, dust mites and grass pollens). In some food allergy may make the eczema worse. If foods do trigger the eczema, it is often only one or two rather than many. Removal of the food will sometimes result in improvement but will not cure the eczema. As foods are not the basic cause of eczema, avoiding a food may not make any difference.
If a food allergy is making the eczema worse what are the symptoms?
There are 2 main ways a food allergy may make the eczema worse:
1. Quick reaction with redness and itching of the skin within an hour or two after eating the food. Children with these reactions will usually have a positive skin prick test or blood test as they have developed IgE allergy antibodies.
2. Delayed reactions when the eczema may gradually get worse (more redness itchiness) over 24 -48 hours after eating the food. These reactions are thought to be due to immune cells in the skin (T cells) reacting against the food. IgE antibodies do not cause these reactions and therefore skin prick tests are not very helpful.
How are these delayed reactions diagnosed?
There are no good tests to know whether foods cause your child a delayed reaction. Your doctor will use your child’s history of possible reactions and a trial of eliminating the suspected food(s). If there is major, improvement the food should continue to be avoided. In a number of cases, the result of removing food(s) from your child’s diet may be unclear and it may be necessary to try the suspected food and see if the eczema gets worse.
What foods are most likely to make eczema worse?
The foods most commonly found in both delayed and immediate reactions are cow’s milk, hen’s egg, wheat and peanuts.
My child develops an eczema rash around the mouth after eating certain foods. Is this food allergy?
This is called perioral contact dermatitis. It is seen after eating acidic fruits and vegetables like orange, tomato and strawberries and is one of the most common food reactions. If a food does this, it can be avoided. Allergy testing is not necessary. The foods may be avoided if the dermatitis around the mouth is severe, but if the reactions are very mild and disappear quickly, removal of the food from the diet is not needed.
Why not just remove all the foods that show up on an allergy test?
Many children with a positive allergy test can eat that food without a problem. Removing many common foods like wheat, milk, soy and egg from the diet is hard to manage, particularly as your child grows older. Food allergies are most likely to make eczema worse in young (preschool) children and often become less and less relevant in older children and teenagers. It is important not to avoid a food forever just based on an allergy test unless it is clear your child’s eczema gets worse when the food is eaten.
There is another reason why it may not be a good idea to remove every food that shows up on an allergy test. There are a number of cases when a child has had a severe allergic reaction to a food that they used to eat safely after they had stopped eating this food when they had a positive allergy test. Continuing to eat a food (if it is not making the eczema worse), even if the allergy test is positive, might actually prevent a more severe allergy developing.
If egg makes eczema worse is this due to the white or yolk?
Allergy can occur to both egg white and yolk. Egg white allergy is more likely to make eczema worse. If your child needs to avoid egg, it is easier to avoid both egg yolk and egg white. Raw egg is more likely to cause immediate reactions than cooked egg as some of the parts of the egg that cause allergy, are altered by heat.
What about foods with a label that says "may contain traces"?
Many foods carry a warning on the label "may contain traces of ". This usually means that the food is made in a factory that also makes other foods that contain the listed food. Any possible trace would be so small that it is very unlikely to make the eczema worse. In general, foods labelled this way do not need to be avoided as part of an eczema diet. However if your child has had a severe allergic reaction (anaphylaxis) to a food you should discuss what to do about these foods with your doctor.
Can my child grow out of the allergy to foods?
Yes. As your child grows out of the eczema, the food allergy will usually improve as well. Eczema often will get better as your child gets older.
Could artificial preservatives or colourings or natural salicylates and amines be causing the eczema or making it worse?
There is some suggestion that artificial colourings and preservatives may make eczema worse in a very small proportion of children with eczema. There is no allergy test for colourings and preservatives. There is no evidence that natural salicylates and amines should be avoided.
What is the role of very restricted diets?
Sometimes your doctor may advise a trial of a strict elimination diet. Such diets are limited to only a few meats (e.g chicken and lamb), a few vegetables (e.g broccoli pumpkin) a few fruits (pears, apples) a cereal (rice) and only water or rice milk to drink. These diets may be used as an initial step to decide whether food allergy is making the eczema worse. The diet is usually tried for 4-6 weeks initially and should not be continued past 6 weeks unless there is a great improvement in the eczema and your doctor has advised that the diet should continue. In general, they are difficult to adhere to. If there is no improvement this suggests that the foods removed are not making the eczema worse. If there is improvement foods are then added back at a rate of 1-2/week. This process and diet will need supervision by your doctor and a dietician.
Where can I find more information on the Internet?
- The Australian Society of Clinical Immunology and Allergy (ASCIA) website contains useful information on eczema written by Australian specialists: www.allergy.org.au
- DermNet NZ the web site of the New Zealand Dermatological Society has information about allergic skin diseases and eczema:www.dermnetnz.org
- The Sydney Children’s Hospital Network website contains fact sheets similar to this one on a number of aspects of allergic disease: www.schn.health.nsw.gov.au/parents-and-carers/fact-sheets