It's thought that many of the lifestyle choices we make today - our housing, diet, and more hygienic environment for instance - may have added to the increasing numbers of people with asthma over the past few decades. Some researchers are currently investigating the theory that improved hygiene conditions have reduced the number of childhood infections. Fewer infections may mean the immune system doesn't develop as well. This lowered immunity can increase the risk of asthma. Environmental pollution, including traffic fumes and chemicals from power plants, can also make asthma symptoms worse and may play a part in causing some asthma.
What's the difference between a 'cause' and a 'trigger' of asthma?
When we talk about the 'cause' of asthma, we mean the underlying reason why you get it in the first place. There are different theories to explain what these possible causes are (as explained above) but if you've got asthma, it's impossible to know for certain what caused it in your individual case.
When we talk about an asthma 'trigger', we mean anything that starts your asthma symptoms or makes your asthma symptoms worse. You may find, for example, that visiting someone with a pet or spending time in a dusty room sets off your symptoms. Other common triggers include exercise, pollen, cold weather or cigarette smoke. You can find out more about asthma triggers and, importantly, how to manage them here.
When does asthma appear?
Asthma can appear at any age. Symptoms usually start during childhood, but it's not uncommon for adults to get it. Some adults develop it after a viral infection. If you get asthma in adulthood, it's known as 'adult-onset' or 'late-onset' asthma. Certain things found in the workplace, such as chemicals or dust from flour or wood, can also lead to asthma symptoms. This is known as occupational asthma.