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What causes allergies?

Published on April 11, 2018

What causes allergies?

When substances such as these cause an allergy, they are called allergens. An allergic reaction occurs when your body becomes overly sensitive to an allergen, causing your immune system to react and result in allergy symptoms. This can occur whenever the allergen is breathed in, ingested or comes into contact with your skin, depending on what it is.

Allergens cause the body to release large amounts of histamine, a chemical that causes the tissues in the body to swell, leading to symptoms. Many allergy medicines work by reducing the amount of histamine produced during an allergic reaction, hence the name ‘antihistamines’.

Dust mites

Dust mites are tiny creatures that cannot be seen with the naked eye and live in most areas inhabited by people. Dust mites are usually found in high numbers in mattresses, pillows, linen, carpets and curtains. An allergic reaction is triggered by exposure to the mites and mite proteins.

Allergic reactions are dose related, therefore the less dust mites in your home environment, the less likely you are to experience an allergic reaction. It is virtually impossible to eliminate all dust mites in your home, but fortunately there are several ways to minimise their numbers including:

  • Cover mattresses and pillows with mite resistant covers
  • Wash linen weekly in water hotter than 55°C
  • Reduce humidity in the house and remove rugs and carpets if you can
  • Vacuum weekly, including mattresses and upholstery to help keep dust mite numbers down. If you are allergic to dust mites, consider having someone else do the vacuuming or if you do it, wear a mask, as mite material is disturbed by vacuuming and may stay in the air for as long as 20 minutes

Pet dander

Pet dander refers to the shed skin cells of animals such as dogs and cats. Pet allergies are relatively common. Between 15% and 30% of people with allergies will also have an allergic response to cats and dogs. People with pet allergies have sensitive immune systems that react to harmless proteins found in dander, pet saliva or urine. Contrary to popular belief, pet hair itself is not an allergen, but it may collect dander.

Unfortunately for animal lovers, avoiding exposure to the problem animal is the best way to avoid allergy symptoms. However, if this is not possible, try the following suggestions to minimise allergic reactions:

  1. Bath your pet frequently
  2. Clean its kennel, bedding or litter box on a regular basis. Even better than this is to ask a family member or friend without allergies to do it for you
  3. Remove carpets and replace them with wooden, tile or linoleum flooring
  4. Consider getting rid of curtains, horizontal blinds and upholstered furniture
  5. The best place for your pet to live if you have allergies is outside. When this is not feasible, consider establishing certain rooms in the house, such as your bedroom, as pet free zones.


Mould is commonly found both indoors and outside, and grows in damp, poorly ventilated areas. In sensitive people, mould may trigger an allergic reaction and symptoms such as sneezing, coughing and a blocked or runny nose. If you see or smell mould anywhere in your house, remove it straight away. Try and find the source of the moisture supporting its growth. Kitchens, bathrooms and laundries are the most common areas of the house that mould grows in because of condensation and a lack of airflow. One of the best ways to discourage mould from growing is to increase ventilation in the problem area, therefore open as many doors and windows as possible.


Pollens are one of the most common causes of allergies. Some people are allergic to pollen from trees, grasses, weeds and flowers. This type of allergic reaction is known as hayfever. Symptoms include sneezing, a blocked and runny nose, and eyes that sting and itch, and are swollen and watery.

One in four people in Australia and New Zealand are affected by hayfever, making it a common problem. It can have a significant impact on quality of life, causing fatigue, poor learning and substandard work performance.

For more information, ASCIA website.


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An allergy is a disorder in which the body becomes overly sensitive to a particular substance, known as an allergen….

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