Food Allergies in Children

This page is about food allergies which are increasingly common and are said to occur in 1 in 20 of children.

A child may be allergic to any number of foods. Some children have allergies to multiple food and some children are allergic to only one particular food.

What are the types of food allergy?

Food allergy is broadly divided into groups depending on the mechanism of the allergy. So allergies to food may be:

• IgE mediated allergy - This is the common type of allergy and involves an antibody in the body called IgE which reacts with the food causing an outpouring of chemicals, including histamine, causing the allergic reaction. Read more. These reactions are usually the easiest to diagnose as they occur within minutes up to an hour after the food is ingested.
• Non IgE mediated allergy - this includes cow's milk protein intolerance, often seen in babies, and some other Food Protein Induced Enterocolitis syndromes (FPIES) - where there is an upset tummy hours after ingestion of the food. This is an immune problem but the IgE antibodies in the body are not involved. The reaction may be a worsening of a skin rash, like eczema, or some type of tummy upset, including vomiting, diarrhea or constipation. Your child may also be failing to thrive (putting on weight)
• Food intolerance, which can be immune mediated such as celiac disease, or non-immune such as lactose intolerance

What are the common foods that cause allergy in children?

Most children who are allergic to a food are allergic to one of the following:

• cow's milk (and dairy products)
• egg
• wheat
• soy
• peanut
• tree nuts, eg. cashew
• fish
• shellfish

Children may also be allergic to other foods, including fruit.

Some children have Oral Allergy Syndrome:

• in some individuals who are allergic to pollens (eg. birch), when they eat certain raw fruit or vegetable, they get a reaction involving mainly the mouth, with itching and swelling of the lips and tongue - it is usually short-lived
• cooking the fruit or vegetables usually does not result in an allergic reaction
• sometimes symptoms get worse if the person exercises after eating the raw fruit or vegetable

Some children are allergic to raw or lightly cooked food but can tolerate the food when it is heated. This is because the heat changes the shape of the protein and so the food protein can't set up the allergic reaction. This happens particularly with egg and milk allergy. However, dry roasting peanuts makes them more likely to cause an allergic reaction.

What symptoms do food allergies cause?

The symptoms of food allergy include:

• skin reactions, such as hives, urticaria, itching and flushing
• nasal congestion or itchiness, runny nose or sneezing
• itchy or teary eyes
• intestinal symptoms, such as nausea, vomiting, colic, abdominal pain or diarrhea
• itching or tingling or swelling of the lips, tongue or inside of the mouth
• chest tightness or wheezing
• worsening of eczema
• failing to gain weight
• anaphylaxis - this is the most severe type of allergic reaction. It involves a skin reaction but also breathing difficulties and/or shock. Read more

Do the symptoms of food allergy get worse the next time you have that food?

Generally speaking, repeated exposure by a child to food he is allergic to does not lead to an escalation of symptoms. So your child is unlikely to have a severe reaction to a food if he has not already had one in the past with that food.

How do you test for food allergies?

• The most important thing in determining what has caused a food allergy is taking a good history (story) of what happened.

• The gold standard for food allergy testing for all types of allergy is a food challenge. A food challenge involves:

• seeing the symptoms stop when the food is removed from the diet
• seeing the symptoms return when the food is re-introduced into the diet
• IgE mediated reactions tend to occur within 15-30 minutes after the food is ingested so it is often easier to pinpoint the allergen. Some children start to get a rash as soon as the food touches the lips.

• Skin prick tests may help identify allergens in IgE mediated allergens as can blood tests (RAST or EAST) - having a positive test does not always mean that there will be an actual reaction when the food is eaten although strongly positive tests are more likely to correlate with actual allergy.

• For non IgE mediated food reactions, some centers have patch testing which can be helpful. Otherwise, the diagnosis is made from the history and what happens when the food is eaten (food challenge).

• For food intolerance such as celiac disease and lactose intolerance, there are specific tests - a blood test or biopsy for celiac disease, and a stool test looking for sugars to diagnose lactose intolerance.

What is the treatment of food allergies?

If your child is allergic to a food, that food should be removed from your child's diet. If your child is on quite a restricted diet because of multiple food allergies, then you should see a dietician to ensure your child is receiving the correct nutrition.

If the food causes an itchy rash, (urticaria), then you might have Cetirizine or another anti-histamine at home that you can give, should your child inadvertently consume the food.

If your child has had an anaphylactic reaction to the food, then you should have been instructed on the use of Epinephrine and you should use this.

Should I exclude foods if the skin prick test shows a reaction?

Not necessarily. If a skin prick test is positive, it means your child has reacted to that food protein on the skin - it doesn't necessarily mean your child will react to the food if eaten. The larger the skin reaction, the more likely your child will actually be allergic to the food.

If skin prick tests are positive, it is important that you only exclude that food if a reaction is likely. So a small skin prick reaction to a food your child seems to have no trouble with does not mean that your child is allergic and you should not exclude that food from the diet. Only exclude foods if there is a very large reaction and there is a supporting history (so there has been a reaction after that food).

Excluding foods on the basis of positive skin prick tests can lead to your child becoming undernourished and this may not be necessary as you child may not even have an allergy to that food.

If your child is on a very restricted diet because of allergy, you should see a dietician to ensure adequate nutrition for growth and development.

Will my child grow out of his food allergy?

Most children do grow out of food allergy usually by school age. Some food allergies, particularly peanut and other nut allergies, can last forever.

Once your child is about 2 year old or so, it is worthwhile to try giving the food to your child every 6 months or so, as long as there is no history of anaphylaxis (in which case, you should only give the food under medical supervision).

Is eczema caused by food allergies?

In most cases of eczema, there will not be any food allergy. However, in some infants, particularly young babies with severe eczema, allergy may be a factor.

In these cases, skin prick tests may be positive and even if they are not, it may be worthwhile trying an elimination diet (so give an extensively hydrolysed formula) for 4 weeks to see if there is improvement. If no improvement occurs, allergy is unlikely to be contributing to the eczema. If there is improvement, foods need to be introduced back into the diet one at a time until you know what the offending food is. The most likely foods will be milk, egg, soy and wheat.

Is colic caused by food allergies?

In most cases, colic is not caused by food allergies. In babies who have a history of allergy who are not breast-fed, it may be worthwhile trying an extensively hydrolysed formula (formula with the protein broken down already) for 2 to 4 weeks - if there is no improvement after this time, allergy is not a cause for the colic and you should return to the baby's usual formula.

Can I prevent food allergy in my baby?

If your child is at high risk of allergy, so there is a strong family history of allergy, you can do the following:

• breast feed your baby for at least 4 - 6 months
• if breast feeding is not possible, use a partially or extensively hydrolysed formula
• do not introduce solid food before 6 months of age
• avoid peanut and shellfish for the first 2-4 years of life
• do not smoke during pregnancy or after the birth of your child

The following are not recommended to prevent allergy as there is no evidence for them:

• food avoidance during pregnancy or lactation
• soy or goat's milk instead of cow's milk
• giving hydrolysed formula to babies where there is no family history of allergy