Child Allergy

Child allergy occurs commonly. Allergy may be to food, pollens and dust (especially house dust mite), insect stings, pets or medicines.

This page contains information on the causes of allergy and general information on allergy including anaphylaxis, as well as linking to pages on specific types of allergy.

To answer a specific question, click on a link below or just keep reading for an overview.

To go to links for specific allergies, click here

To view the Useful Allergy Resource List, click here


What causes child allergy?

In an allergic person, the immune system recognizes some proteins as foreign. These proteins are called allergens. An allergen may be a food, an airborne particle like pollen or dust or a medicine.

In an allergic person, the body thinks the allergen is a danger so attacks it with antibodies. These antibodies react with other cells releasing chemicals that set up the allergic reaction. These chemicals include histamine.

This is called an IgE mediated allergy.

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Are all allergies IgE mediated?

No, there are other types of child allergy as well as IgE mediated ones which have different mechanisms - particularly food allergies.

The types of food allergy include:

  • IgE mediated allergy
  • 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.
    Celiac disease is another type of non IgE mediated allergy
  • Food intolerance, such as lactose intolerance

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Why are some children allergic?

Allergies generally run in families so the most likely reason your child is allergic is that it is in your family. Asthma, eczema and hayfever also run in families and are often seen in allergic individuals. If these diseases run in your family, you will be described as atopic (or suffering from atopy). Child allergy is more common in atopic families.

Allergies are more common these days and it has been postulated that this is due to houses being cleaner and children being exposed to less germs (which means their immune system develops differently and is more likely to become allergic).

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What is an allergic reaction?

Child allergy reactions can vary but will mostly affect the skin, gut and respiratory system and in some cases the circulation.

Some allergens, such as pollens, cause a runny nose, itchy eyes and sneezing. So these are upper respiratory symptoms.

Other allergies can affect the skin, so cause an itchy skin rash that is often described as hives or welts - the medical term is urticaria. Some allergies make eczema worse.

Some allergies affect the gut causing tummy upset, such as tummy pain or vomiting. Babies with cow's milk protein intolerance can have blood in the stool.

The most serious allergic reaction is anaphylaxis (or an anaphlylactic reaction) which affects the circulation or the lower respiratory system causing wheezing and breathing difficulties.

So the systems that may be affected include:

  • Skin - urticaria, angioedema (swelling of lips, tongue, eyes), eczema
  • Gut - diarrhea, vomiting, abdominal cramps
  • Respiratory system - cough, wheeze, stridor, sneezing, runny nose. It is rare for food allergy to cause respiratory problems without involvement of other systems
  • Cardiovascular system - low blood pressure, collapse

When the skin or gut are involved, the reaction is called a generalised allergic reaction

When either the lower respiratory tract or cardiovascular system are involved as well, this is anaphylaxis.

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What is anaphylaxis?

Anaphylaxis is the most severe form of child allergy and can be fatal.

Only a few children with allergy will have an anaphylactic reaction. Children usually have anaphylactic reactions to food.

Anaphylaxis is usually fairly immediate after the allergen is ingested (within 15-30 minutes) and usually presents with at least 2 of the following systems affected:

  • skin - so itchy rash, swelling of lips, swelling of the eyes, swelling of the tongue
  • breathing - so wheeze or stridor (both noisy breathing), struggling to breathe, unable to speak
  • shock - pale and sweaty with fast weak pulse, loses consciousness

If you are worried about your child's allergic reaction, call an ambulance immediately. If your child has an EpiPen (or other Epinephrine (Adrenaline) auto-injector), use it immediately.

Click here for an example of an anaphylaxis emergency plan

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Will my child grow out of their allergy?

Most children will grow out of food allergies but they may develop other allergy-like diseases instead as they grow older, like hayfever and asthma. Some allergies are life-long.

There is a theory of the atopic march - which means that children who are atopic (allergic individuals who are prone to asthma, eczema and hayfever) have eczema or food allergy when infants and then later develop asthma or hay fever later in life.

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How do you test for allergies?

The most important thing in determining what has caused child allergy is taking a good history (story) of what happened. IgE mediated reactions tend to occur within 60 minutes after the allergen contact.

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 with the allergen although strongly positive tests are more likely to correlate with actual allergy.

Click here for information on food allergies - food challenge is also used for testing in these children.

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What is the treatment for child allergy?

The first thing is to avoid the allergen, so if your child has a peanut allergy, avoiding peanuts in the diet is the first thing to do to prevent a reaction.

If your child has had an anaphylactic reaction in the past or has asthma that requires preventative treatment and has allergy, then your child will need Epinephrine (Adrenaline) that can be injected. There are auto-injector devices, such as EpiPen and AnaPen, that are easy to use in an emergency. You will also need to have a written action plan, developed with your doctor.

Click here for an example of an anaphylaxis emergency plan

For children who do not have anaphylactic reactions but have an itchy skin rash, the treatment will depend on the symptoms but if your child gets an skin rash, an anti-histamine, like Cetirizine, will be useful. Oral steroids may also be given.

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How can I prevent child allergy in future children?

The following gives an outline of evidence as it currently stands on preventing child allergy:

  • Pregnancy
    • stop smoking
    • there is no evidence to support restricting your diet
    • there is no evidence to support fish oil supplements - although they won't hurt your baby
    • there is no conclusive evidence to support probiotics - although they won't hurt your baby and more research is underway
  • Newborn Babies
    • Breast feed exclusively for the first 4 - 6 months if possible
    • Don't introduce solids before 4 - 6 months. Once you start weaning, try a new food every 2-3 days according to if your baby is ready and what the family eats. Introduce one new food at a time so that any reactions can be readily identified.
    • There is no evidence to support delaying introduction of some foods, such as dairy, egg, beyond 6 months when your baby is weaned
    • There is no need to get rid of pets unless there is a clear allergic reaction

For some things, like probiotics and fish oil, although there is no evidence that they reduce allergy, pregnant women can take them if they feel they benefit their overall health as they will not harm your baby. Future studies may show some benefit from probiotics.

So to summarize, to prevent child allergy you, as a parent, can do the following:

  • stop smoking if you do
  • breast-feed for as long as possible and preferably till 6 months of age
  • don't introduce solids before 4 months of age. Most babies will be ready for solids sometime between 4 and 6 months. Once on solids there is no reason to delay introduction of any foods. In fact, the most recent advice on peanuts is that these foods should be introduced early after weaning and before a year of age even in babies with severe eczema - to read more, click here

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Useful Resources

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  • Australasian Society of Clinical Immunology and Allergy
  • Prescott S, Tang M. Allergy Prevention in children. MJA 2005; 182 (9): 464-467
  • American Academy of Allergy, Asthma and Immunology. The Allergy Report
  • Management of atopic eczema in primary care. A national clinical guideline - Scottish Intercollegiate Guidelines Network (SIGN); 2011

To go to the top of the Child Allergy page, click here

To go to the Skin Prick testing page, click here

To go to the Food Allergies page, click here

To go to the Egg Allergy page, click here

To go to the Milk Allergy page, click here

To go to the Peanut Allergy page, click here

To go to the Dust Mite Allergy, click here

To return to the Home page, click here

Last reviewed 18 March 2016

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Dr Maud MD

Dr Maud MD (MBChB, FRACP, FRCPCH), a specialist pediatrician, provides health information and medical advice for parents of babies and toddlers. Read more about Dr Maud.

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