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Written by Dr Angela Simpson, specialist registrar respiratory medicine
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Asthma is a chronic lung disease that causes sufferers
to have repeated attacks of:
In people with asthma, the linings of the air passages (bronchi and bronchioles) are inflamed. Some asthma sufferers have allergies. In these people, airway inflammation occurs because they are exposed to items in their environment to which they are allergic, for example house dust mites, cats and dogs. This is known as atopic or allergic asthma. Other people with asthma have no such allergies and the cause of their airway inflammation is unclear (known as non-atopic asthma). In both types of asthma, the inflamed air passages can be irritated by lots of 'triggers'. The triggers cause the airways to narrow, which results in an asthma attack. These triggers include:
Some people with allergies are not aware of them. If you have asthma and think you have allergies and would be interested in allergen avoidance, it is worth asking your GP if he can arrange for patch testing (skin tests) or blood tests to confirm your allergies. Avoiding the things that trigger your asthma is only one part of asthma management. It should be used to complement the asthma medication and advice provided by your doctor. Allergens
House dust mites are arachnids (related to spiders) and are about 0.3mm long, so cannot be seen with the naked eye. They feed on old human skin scales and like to live in a humid environment. They can be found in most homes in the UK - usually anywhere that is warm, damp and collects dust, such as: 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.
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:
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.
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:
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.
Many people with asthma find that exercise triggers their asthma symptoms. Nobody knows for certain why this is. It may be because the amount of air going in and out of the lungs increases during exercise, thereby causing cooling and drying of the airways, which then triggers asthma symptoms. It is important, however, that people with asthma continue to exercise and keep fit and most people with asthma should be capable of normal activities. You should discuss your exercise programme with your doctor or nurse when your asthma management plan is prepared. It may be that taking your 'reliever' inhaler before exercise will be enough to help with your symptoms. Some people who take regular exercise, or plan to increase their exercise programme, may require an increase in the dose of their preventer medicine. For more information read the factsheet about asthma on exercise.
Viruses cannot generally be avoided and many patients with asthma will experience an exacerbation of their symptoms when they get a cold, which may last for a few weeks. Asthma patients should take particular care to check their peak flow when they get a cold and use this information to follow their asthma management plan. This will often involve a doubling in the dose of the inhaled steroid (preventer inhaler) for several weeks, as the symptoms often take a while to settle down. The Chief Medical Officer, who advises the government on issues of public health, recommends that those with chronic respiratory illness, including asthma, should have the flu vaccine each year.
In some patients with asthma (particularly in those with nasal polyps) taking aspirin (eg Disprin) or related medicines called non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen (eg Nurofen) or diclofenac (eg Voltarol)) could make their asthma worse, sometimes causing a very severe attack. The component of aspirin that can cause asthma in some people is also found in many processed foods as well as fruits and vegetables. In a minority of patients who are very sensitive to aspirin a strict diet may need to be followed to improve asthma symptoms. If the doctor diagnoses aspirin-sensitive asthma, the help of a qualified dietitian may be required to plan your diet.
There are many reasons why people with asthma should not smoke. Cigarette smoke contains many chemicals that irritate the airways, making all smokers more susceptible to chest infections than non-smokers. Cigarette smoking causes cancer and other lung diseases such as chronic bronchitis or emphysema (now known as COPD - chronic obstructive pulmonary disease). COPD is more likely to develop in asthmatics who smoke than in non-asthmatics. In addition, children with asthma who are exposed to cigarette smoke at home have worse lung function and require more asthma medication than asthmatic children who live with non-smokers.
Air pollution comes mainly from motor vehicle exhausts, power stations and industrial plants and factories. It is composed of ozone and oxides of nitrogen and sulphur. Although there is little evidence that air pollution causes asthma, exposure to air pollution does make asthma symptoms worse for many sufferers. Pollution, however, is difficult to avoid. |
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| Last updated 01.08.2005 |
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