Asthma - reducing your exposure to triggers

House dust mites produce allergens, which are proteins, and some of these are found in high concentrations in their droppings.

Many allergic asthmatics are sensitised to these proteins and exposure to them can cause both airway inflammation and can act as a trigger for an asthma attack. Because the mites cannot be seen but are everywhere, most asthmatics are exposed to these allergens all the time in their homes without realising that this exposure may be making their asthma worse.

To avoid house dust mites:

At night, in bed, we spend on average eight hours in close contact with large amounts of house dust mite allergen. Measures to reduce exposure to the allergen in bed are probably the most important.

Although vacuum cleaners that do not contain filters and double thickness bags can remove mite allergens from carpets, they should not be used by people with asthma. This is because they tend to release the mite allergens into the air, and make an asthmatic person more likely to have an asthma attack.

Sensitised patients should use vacuum cleaners with built-in HEPA filters and double thickness bags, and ensure they service the vacuum cleaner regularly.

Reducing humidity in the home has not been shown to be effective in the treatment of asthma in the UK, but may work in countries with different climates.

Killing house dust mites with chemicals (acaricides) or by freezing them with liquid nitrogen works in the laboratory, but has not been shown convincingly to improve asthma symptoms when it is used in the home. Acrosan is the most commonly used acaricide and Allergy UK will be able to give information on where it is available.

Pets

Many asthmatics are allergic to the furred pets that they keep, particularly cats and dogs. Pets shed allergen with their fur and dander and, before long, it is spread all around the house.

The presence of the pet in the house can be both a cause of the airway inflammation and a trigger to asthma attacks. The best way to deal with this problem is to remove the pet, but even after the pet has gone and the house has been thoroughly cleaned, it can be many months before the levels of allergen return to those found in homes without pets.

For those who insist upon keeping a pet, some measures have been shown to reduce the levels of pet allergen in the home and some evidence has been collected to show that this may be of benefit in asthma. These measures include:

Food

Many people believe they are allergic to certain foods, but true food allergies are relatively rare and affect about 5 per cent of children and 1 per cent of adults. Some people with asthma are allergic to foods such as:

As the symptoms of the allergy generally start very soon after eating the food, and are often severe, the person makes the connection and then takes appropriate steps to avoid the food. It is often helpful for someone like this to see an allergist, so that:

In some patients with chronic, severe asthma, some foods may exacerbate the condition, but identifying the culprits can be difficult. In severe cases, people may be admitted to hospital for an exclusion diet (eating only a few very simple foods), to see if this improves their asthma. Thereafter, foods are gradually reintroduced to identify the agents that cause the asthma to get worse. Foods such as milk, eggs and wheat are sometimes associated with this type of allergy.

Pollen

Some asthmatics notice a worsening of their symptoms in the pollen season, usually from March to September. Grass and tree pollens are also difficult to avoid, but the following measures may be helpful in some cases:

The workplace

Some people with asthma are exposed to substances at work that make their asthma worse; this is known as 'work-exacerbated asthma'. Others develop asthma because of exposure to substances at work, usually within the first few months or years of employment ('occupational asthma' or 'work-induced asthma').

It is important to recognise occupational asthma because:

In general, for occupational asthma, the shorter the duration of exposure to the substance, the better the chance of a full recovery. Occupational asthma can sometimes be difficult to diagnose and may require help and advice from an expert in occupational respiratory medicine.

The jobs that are most commonly associated with occupational asthma are:

Many other substances can cause occupational asthma, but the vast majority of people doing these jobs will not get asthma. Treatment of occupational asthma depends upon the specific job. Changes in the work practice, work environment or the job itself, may be needed to avoid exposure.

Non-specific allergens