What is an allergy?

An allergy is when your immune system reacts to something that is harmless to most people.

Substances that cause allergies are called allergens. Common allergens include:

• foods (including egg, fish and shellfish, nuts, eggs, wheat, dairy, soy)
• cat and dog dander
• grasses and pollen
• dust mite
• some medicines
• insect and mite bites
• latex (rubber)

What is a hypersensitivity reaction?

A hypersensitivity reaction is an overreaction of your immune system to something that would not usually cause an immune response. This leads to allergy symptoms.

There are different types of hypersensitivity reactions.

• Type I reactions usually develop within a few minutes of exposure to an allergen but can occasionally develop over a few hours. They are mostly mild, but can sometimes develop into a severe reaction called anaphylaxis.
• Type II and III reactions occur when something triggers your body’s own immune system to attack parts of your body. This can cause autoimmune diseases that range from mild to severe.
• Type IV reactions, also called ‘delayed hypersensitivity reactions’, occur 12 to 72 hours after exposure to the allergen. Examples of type IV reactions include contact dermatitis, some lung conditions, type I diabetes and organ transplant

What are the symptoms of allergies?

Symptoms of allergies depend on the type and severity of your allergy and can range from mild to life-threatening.

Symptoms or conditions caused by allergies include:

• hay fever (runny nose, itchy and watery eyes)
• eczema (dry, red, itchy skin)
• hives (a bumpy skin rash)
• asthma (wheezing, coughing and difficulty breathing)

A severe type of allergic reaction called anaphylaxis can cause:

• breathing problems
• swollen tongue, lips and face
• swelling or tightness in the throat
• difficulty talking or a hoarse voice
• wheezing and coughing
• abdominal pain and vomiting
• dizziness and possible collapse

Watch this video from Allergy & Anaphylaxis Australia for more information about how to recognise signs and symptoms of an allergic reaction.

Video not working? View it here.

When should I see my doctor?

Anaphylaxis needs immediate treatment with an injection of adrenaline. If you or someone with you is having an anaphylactic reaction and they have an adrenaline autoinjector (brand names include EpiPen and Anapen), give them a shot of adrenaline.

Learn about first aid for anaphylaxis and how to use an adrenaline autoinjector.

See your doctor if you have mild or moderate allergy symptoms. There are treatments available and things you can do to help.

How are allergies diagnosed?

Your doctor will ask about your symptoms and perform a physical examination. They will ask about your overall health and the health of your family.

Your doctor may suggest allergy testing. These tests can help find out what you are allergic to.

How are allergies treated?

Treatment for allergies depends on the type and severity. Talk to your doctor about what treatments may suit you.

Your doctor may refer you to an allergy specialist for further assessment and treatment.

Medicines

Allergies can be treated with antihistamine medicines. These may be given as a tablet, nasal spray or eye drops.

Corticosteroid medicines are sometimes used to treat allergies. Depending on your symptoms, these may be given as a nasal spray, inhaler or skin ointment.

Immunotherapy

Allergen immunotherapy is a type of treatment for allergies. It helps to stop the body overreacting to allergens.

Adrenaline (epinephrine) for anaphylaxis

Anaphylaxis needs emergency treatment with adrenaline (epinephrine). People with severe allergies should carry an adrenaline autoinjector (brand names include EpiPen and Anapen) at all times.

Allergy action plan

People who have severe allergies should have an allergy action plan to guide them and others on what to do in an emergency.

Can allergic reactions be prevented?

It’s important that people with severe allergies avoid the substances they are allergic to, so they don’t experience a severe allergic reaction, which can be life-threatening.

If you have hay fever or eczema, you can reduce your symptoms by reducing your exposure to allergens that trigger these conditions.

Resources and support

There are guidelines from the Australasian Society of Clinical Immunology and Allergy (ASCIA) on infant feeding and allergy prevention.

Talk to your doctor about steps you can take to avoid and prevent allergies.