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.

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
• Food intolerance, such as celiac disease and lactose intolerance

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).

Allergic reactions can vary. Some allergens, such as pollens, cause a runny nose, itchy eyes and sneezing.

Other allergies can cause an itchy skin rash that is often describes as hives or welts. Some allergies make eczema worse.

Some allergies cause wheezing and breathing difficulties and some cause 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).

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 and occurs when there are 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 auto-injector), use it immediately.

Click here for an example of an anaphylaxis emergency plan

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 hayfever.

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 15-30 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.

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, 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.