Allergy

Allergy

Allergies happen when your child's immune system overreacts to a substance (called an allergen) which is harmless to most people.

Key points to remember about allergy

  • allergies happen when your child's immune system overreacts to a substance (called an allergen) which is harmless to most people
  • every time your child has contact with that allergen they will experience symptoms of an allergic reaction, usually within a few minutes
  • environmental/airborne allergens (such as house dust mites, pollen and pets) can cause mild to moderate symptoms
  • food allergy (and also bee or wasp venom, and latex) can cause mild to severe symptoms
  • anaphylaxis is a life-threatening  allergic reaction which requires urgent medical treatment

What is an allergy?

An allergy occurs when a person's immune system overreacts to a substance (allergen) in the environment by making allergic antibodies (IgE) against the allergen. There are many types of allergens found in our environment. The most common of these are:

  • airborne allergens that come from dust mites, cats and dogs, pollen, moulds
  • food allergens
  • insect venom
  • other things such as drugs or latex

Once your immune system has made IgE against an allergen, coming into contact with that allergen can result in an allergic reaction, with symptoms that can range from annoying to life-threatening.

Who gets allergies?

The tendency to develop allergies is usually passed down through your genes. But, not everybody in a family will have the allergies. Members of the same family may have allergies to different things and some people may develop allergies when no other member of the family has any. When a child is allergic to one thing, it is likely that they may be allergic to other substances as well.

What are the signs and symptoms of allergies?

The symptoms of an allergy vary according to what a person is allergic to.

Airborne allergens such as pollen usually cause 'hay fever' (allergic rhinitis). Children with 'hay fever' may have seasonal symptoms with a runny, itchy nose or eyes and sneezing during grass pollen season. Children who are allergic to dust mites may have year-round 'hay fever', with a runny or blocked nose and sneezing, often worst in bed. Airborne allergens can also contribute to the symptoms of asthma and eczema.

Children with food allergies get symptoms most often on eating the food that they are allergic to. Symptoms of food allergy can include skin rashes (such as hives or welts), swelling of the face, lips and eyes, and gastrointestinal symptoms such as stomach pains, vomiting and diarrhoea. Some children may have a severe reaction with breathing problems (for example, cough and wheeze) or collapse. This is called 'anaphylaxis' and can be life-threatening.

How are allergies diagnosed?

Your doctor usually diagnoses allergies once they have listened to your story and examined your child.

Environmental allergies may be obvious from your child's story (for example, your child gets itchy and sneezy every time they pat a cat). But sometimes, your child might need testing for these allergies.

If food allergy is suspected, your child may need an allergy test (skin tests or a blood test for specific allergic antibodies, previously called a RAST) to confirm what they are allergic to. This is to make sure you know what foods your child needs to avoid. In some cases, your child might need to go to a paediatric clinic or specialist.

How do I manage my child's allergies?

Once your family doctor, paediatrician or specialist diagnoses your child's food allergy, managing it includes avoiding the allergen. Make sure your child also avoids all the different products containing the allergen and the different forms it might come in. Families often need help from a dietitian to do this.

All children with food allergy need to have a management plan explaining how to manage an allergic reaction after accidental food exposure. Children with food allergy need follow up to see whether their food allergies are going away. ASCIA (the Australasian Society of Clinical Immunology and Allergy) has developed several action plans for use in Australia and New Zealand.

See the various action plans at the ASCIA website.

Some children with food allergy also have asthma. It is important they have asthma medicines and an asthma management plan to keep their asthma under control. Having asthma can make an allergic reaction to food more severe.

Avoidance of airborne allergies is sometimes possible, with advice about this also on the ASCIA website. Medicines may be used to treat allergic rhinitis/hay fever.

What are the most common airborne allergens?

Some of the most common things people are allergic to are carried through the air. These include:

  • dust mites which live in carpets, bedding and upholstery
  • pollens from trees, grasses and other plants
  • animals such as cats, dogs and horses
  • moulds, which thrive in warm, dark, moist places, such as bathrooms, basements and outdoors in compost heaps

What are the most common food allergens?

These include:

  • dairy products such as cow's milk and milk products such as butter and yoghurt
  • eggs
  • nuts and peanuts
  • fish and shellfish
  • sesame
  • soy
  • wheat (which is found in breads and cereals)

What are other common allergens?

These include:

  • insect stings (bees and wasps)
  • medicines
  • latex

What is anaphylaxis?

Anaphylaxis can be life-threatening - it's a medical emergency which needs immediate treatment.

Anaphylaxis is the most severe form of allergic reaction and can be life-threatening. Anaphylaxis is a medical emergency which needs immediate treatment.

What are the signs and symptoms of anaphylaxis?

The signs and symptoms of anaphylaxis include:

  • difficulty breathing/noisy breathing
  • swelling of the tongue
  • swelling/tightness in the throat
  • difficulty talking and/or a hoarse voice
  • wheeze or persistent cough
  • dizziness or lightheadedness
  • loss of consciousness and/or collapse
  • being pale and floppy (in young children)

How long does it take for anaphylaxis symptoms to occur?

The symptoms can occur within seconds of coming into contact with the allergen or can take up to 2 hours to occur.

Can there be any warning signs before anaphylaxis?

In some cases, less dangerous allergic symptoms appear before anaphylaxis. These include:

  • swelling of the face, lips and eyes
  • hives or welts on the skin
  • stomach pain, vomiting

What influences how severe anaphylaxis is?

Several things can influence how severe anaphylaxis is, including:

  • exercise
  • heat
  • in food-allergic people, the amount of allergen they have eaten and how the food was prepared

Severe allergic reactions require urgent medical attention.

This page last reviewed 26 June 2019.
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