What causes allergies?

An allergy starts when your immune system mistakes a normally harmless substance (allergen) for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you’re exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause allergy symptoms.3

Common allergy triggers

Common allergy triggers include:3

  • Airborne allergens, such as pollen, animal dander, dust mites and mold
  • Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
  • Insect stings, such as from a bee or wasp
  • Medications, particularly penicillin or penicillin-based antibiotics
  • Latex or other substances you touch

You might be more likely to develop an allergy if you:3

  • Have a family history of asthma or allergies, such as hay fever, hives or eczema
  • Are a child
  • Have asthma or another allergic condition

Having an allergy increases your risk of certain other medical problems including:3

  • Anaphylaxis. If you have severe allergies, you’re at increased risk of this serious allergy induced reaction
  • Asthma. If you have an allergy, you’re more likely to have asthma. In many cases, asthma is triggered by exposure to an allergen in the environment
  • Sinusitis and infections of the ears or lungs. Your risk of getting these conditions is higher if you have hay fever or asthma

Preventing allergic reactions depends on the type of allergy you have. Some general measures:3

  • Avoid known triggers
  • Keep a diary to identify what causes or worsens your allergy
  • Wear a medical alert bracelet if you’ve had a severe allergic reaction