When talking about diseases, it is important to distinguish between causes and triggers.
A trigger is something which sets off an attack, but which does not make you asthmatic in the first place.
The “trigger factors”, or “triggers”, of asthma are used to describe the things which can cause an attack in someone who already has asthma.
But you hear these words used for the dog to which you may be allergic, or the cat, or the mould on the wallpaper which causes your asthma, or the pollen that cause your asthma, and even about house dust mites. Instead of calling these things causes, which is what they are, people call them “triggers”. They say that your cat is triggering your asthma.
This is a bit like calling an on-coming car the trigger for an accident.
Demoting causes, by calling them triggers, makes people think they are not so important, and that maybe they should just keep using their inhalers instead of making efforts to root out the cause of their asthma and remove these from their environment.
A cause is something without which an effect (such as asthma) will not happen. That is, a cause is something without which you would not be asthmatic. There may be more than one cause for an asthma attack.
We normally think of a trigger factor as something small, which causes something big to happen suddenly. A trigger is a type of cause. But the implication is that the important causes have to be there already if the trigger is to work, and that the trigger is not so important. It is the cause which is important.
For example, if you don’t have asthmatic lungs, or your asthma is really well controlled by treatment, a cold won’t give you any symptoms of asthma.
So in this sense, it is fair to call the cold a “trigger factor”. In addition, if you did not catch colds, this would not stop you having asthma, so in that sense it cannot be called the true cause of the disease.
But if you have asthma whenever you go near dogs, then dogs in the past have been the cause, and a dog now can trigger an attack. In other words, a dog can be a cause of asthma and also a trigger of an attack.
Concentrating only on the triggering of the attacks misses the really important point that contact with dogs was a cause of the asthma in the first place.
Obviously, an asthma sufferer will want to avoid both causes and triggers of asthma, but the causes are more serious. Without the causes, the triggers would do absolutely no harm.