According to the charity Asthma UK, one in five households has someone living with asthma.

No one knows for sure what causes asthma, but we know that you're more likely to develop it if you have a family history of asthma, eczema or other allergies. You're twice as likely to develop asthma if your parents have it.
Modern lifestyles, such as housing and diet, may have also contributed to the rise in asthma over the last 30 years.
Research shows that smoking during pregnancy increases the risk of your child developing asthma. Children whose parents smoke are also more likely to develop it. 
There are many theories about what's caused the increase in people with asthma.
One of the most popular is the 'hygiene hypothesis'. According to this theory, asthma is more common in Western societies. Because Western society is becoming cleaner, we have less exposure to allergens and pathogens.

Smoking and asthma

Hygiene hypothesis

According to the hygiene hypothesis, young children who aren’t exposed to infectious agents, micro-organisms and parasites may be more susceptible to allergic diseases.

When a person with asthma comes into contact with a ‘trigger’, their airways become irritated. The muscles tighten, the airways narrow and the lining of the airways gets inflamed and swollen.

The main symptoms are chest ‘wheeze’ or noisy breathing, chest tightness and breathlessness. You may also develop a cough, particularly at night, but this is more common in children.

Boys under the age of two are more susceptible to asthma because their airways are narrower when they're younger. But they usually grow out of it, whereas girls are more likely to have asthma beyond puberty.

Obesity is thought to make asthma more likely. Symptoms often get better when the person loses weight.

Smoking also has a definite impact. Parents' cigarette smoke will affect their child’s lung function development, and it irritates the airways. People with asthma are advised not to smoke.

Once you have asthma, high levels of pollution and smoking may make it worse. But there's no proof  that these triggers actually cause it.

Treatment

How to help yourself 

If certain things trigger your asthma, such as dust mites, minimise your exposure to them. Put mattress covers on your bed, use a damp cloth when you dust, don't have too many soft furnishings in your house, and put down laminate or wooden flooring instead of carpets.

Asthma triggers include pets, but studies show that getting rid of animals doesn't improve asthma. In fact, the emotional upset of getting rid of your pet may make your asthma worse. Keep your exposure to pets to a minimum in areas such as the bedroom, and don't replace pets when they die.

Asthma medicines

If you have symptoms more than three times a week and you need to use a reliever inhaler (usually blue), also use a preventer inhaler (usually brown). However, if you only have symptoms a few times a week when exercising, you can manage your symptoms safely with a reliever inhaler before you exercise.

Asthma is an inflammatory disease. This means preventative treatment is vital, and you must take it even when your asthma symptoms aren’t present. This will ensure your asthma is well-controlled.

Review your treatment with your asthma nurse or GP at least once a year because you might be able to reduce your dosage of medicine.

Find out more information about asthma treatments.

Fears about steroids

Because asthma is caused by an inflammation of the airways, anti-inflammatory drugs such as steroids are sometimes used to treat it.

You may be concerned about the potential side effects of steroids, such as weight gain, stunted growth (in children) and weakened bones.

The risk of side effects if you or your child are using a steroid inhaler is lower than with steroid tablets because less of the medicine gets into your system. With both steroid inhalers and tablets, the risk of side effects increases if the dose is high and if you use them for long periods.

Generally, if inhaled steroids are carefully prescribed and at the lowest dose needed, the risk of side effects is outweighed by the ability to reduce you or your child's need for steroid tablets. But if you're concerned, discuss the risks of steroid treatment with your doctor.

The many faces of asthma

The many potential triggers of asthma largely explain the different ways in which asthma can present. In most cases, the disease starts in early childhood from 2-6 years of age. In this age group, the cause of asthma is often linked to exposure to allergens, such as dust mites, tobacco smoke, and viral respiratory infections. In very young children, less than 2 years of age, asthma can be difficult to diagnose with certainty. Wheezing at this age often follows a viral infection and might disappear later, without ever leading to asthma. Asthma, however, can develop again in adulthood. Adult-onset asthma occurs more often in women, mostly middle-aged, and frequently follows a respiratory tract infection. The triggers in this group are usually nonallergic in nature.

Typical asthma symptoms and signs

The symptoms of asthma vary from person to person and in any individual from time to time. It is important to remember that many of these symptoms can be subtle and similar to those seen in other conditions. All of the symptoms mentioned below can be present in other respiratory, and sometimes, in heart conditions. This potential confusion makes identifying the settings in which the symptoms occur and diagnostic testing very important in recognizing this disorder.

The following are the four major recognized asthma symptoms:

• Shortness of breath, especially with exertion or at night
• Wheezing is a whistling or hissing sound when breathing out
• Coughing may be chronic, is usually worse at night and early morning, and may occur after exercise or when exposed to cold, dry air
• Chest tightness may occur with or without the above symptoms

Asthma fact

Asthma is classified according to the frequency and severity of symptoms, or "attacks," and the results of pulmonary (lung) function tests.

·         30% of affected patients have mild, intermittent (less than two episodes a week) symptoms of asthma with normal breathing tests

·         30% have mild, persistent (two or mores episodes a week) symptoms of asthma with normal or abnormal breathing tests

·         40% have moderate or severe, persistent (daily or continuous) symptoms of asthma with abnormal breathing tests