Pets

Exposure to pets (eg cats, dogs, guinea pigs, horses, rabbits, mice, rats) at home or work can trigger asthma in some people.

Cats and dogs are a major source of allergens in the home environment. The allergens come from the sweat glands in cats and salivary glands in dogs. As all cats and dogs have sweat and salivary glands there are no breeds that do not contain allergens, although the amount of allergen released can vary between breeds.

As allergens are stuck to the hair and skin of pets, the allergens become airborne when the pet sheds their hair. The allergens can remain airborne for some time.

Cat allergen is especially difficult to remove from houses. It can remain in the house for months after the cat is removed. Cat allergen can be found in places where cats have never lived. For example, it can be carried around on clothing to schools and offices.

The most effective method of allergen avoidance for people with asthma who are allergic to cats or dogs is removal of the pets from the home.

Less effective measures, which have not yet been adequately tested include:

•  keeping pets out of bedrooms and living areas (although it may take weeks after pet removal before allergen levels are reduced)

•  washing pets weekly

•  vacuuming carpets weekly using a high efficiency particulate air (HEPA) vacuum cleaner

•  using HEPA air filters.

Pollen                                     

Allergy to airborne pollen grains from certain grasses, weeds and trees:

•  is common in people with asthma

•  may worsen asthma symptoms during the pollen seasons (usually in spring and early summer or during the dry season in tropical regions)

•  can cause outbreaks of asthma attacks after thunderstorms

•  is usually caused by imported grasses, weeds and trees, which are wind pollinated

•  is not usually caused by Australian native plants (although there are exceptions, such as Cypress Pine)

•  is not usually caused by highly flowered plants as they produce less pollen (which is transported by bees) than wind pollinated plants.

The following measures may help reduce exposure to pollen, but are yet to be proven to improve asthma control. •  Remain indoors during pollen seasons, on windy days or after thunderstorms. •  Avoid activities known to cause allergen exposure – such as mowing grass. •  Shower after outdoor activities where there is high exposure to pollen. •  Use recirculated air in the car when pollen levels are high.

Mould

Living in houses that are damp and have visible mould can increase the risk of wheezing in some people.

If you are allergic to mould, consider:

•  removing visible mould by cleaning with bleach or other mould reduction cleaners

•  ensuring adequate natural ventilation

•  sealing leaks in bathrooms and roofs

•  removing indoor pot plants (which promote mould growth)

•  not working with garden compost or mulch.

The effects of these measures on asthma control are yet to be tested.

Although humidity promotes mould growth, dehumidifiers have been studied and have not been shown to be helpful in asthma control.

Food

Foods are not common triggers for asthma symptoms.  They rarely trigger asthma on its own, but may trigger asthma as part of a generalised severe food allergy reaction involving other symptoms in the skin and gut. This reaction is known as anaphylaxis and it can be life-threatening.  It is rare in adults and uncommon in children.

Food additives and chemicals also rarely trigger asthma. Most adverse reactions to food additives and chemicals are not allergic reactions and cannot be tested for by using skin prick tests or blood (RAST) allergy tests.

If foods or food additives are suspected as triggers for your asthma, you may need to be referred to an allergy specialist for further detailed assessment. If foods are confirmed as triggers, your allergy specialist may recommend a dietitian for advice.