Preventer inhalers

Preventers control the swelling and inflammation in the airways, stopping them from being so sensitive and reducing the risk of severe attacks. 

Outline drawing of a metered dose inhaler. Not everyone with asthma will be prescribed preventer medicine.


The protective effect builds up over a period of time so they need to be taken every day (usually morning and evening) even when you are feeling well.

Preventers do not give immediate or quick relief when you are breathless but instead they reduce long-term inflammation. Preventer inhalers usually contain a low dose of steroid medicine.

There are several kinds of preventers, but they all work in the same way. You will be started on an appropriate level of treatment to get your symptoms under control; once this has been achieved the treatment will be reduced to the lowest possible dose.

Preventers are usually brown, red or orange inhalers.

When are preventers prescribed?

You should be prescribed a preventer if you:

  • are breathless, cough or have a tight chest during everyday activities three or more times a week
  • need to use your reliever inhaler three times a week or more
  • have sleep disturbed by cough or chest tightness each week
  • have bad attacks of breathlessness when you have a chest infection or are in a smoky atmosphere.

What will my preventer do for me?

As the protective effect of the steroid builds up, you will be less likely to have asthma attacks. You will be less likely to be breathless during the day and night and you will not need to use your reliever inhaler as often.

Why is my reliever inhaler not enough?

Reliever inhalers relax your airways, which help breathlessness, but they do not remove airway inflammation. As well as the relaxing effect of a reliever inhaler, you need the anti-inflammatory effect of a preventer. Once airways are less inflamed they are less sensitive to triggers such as cigarette smoke and viral infections.

How long will it take to work?

It may take up to 14 days for your preventer medicine to reduce inflammation and mucus in your airways.

Don't stop taking it if nothing much happens for a few days. Gradually, chest tightness, night cough and wheeze should become less. You should notice that you need to use less reliever inhaler.

When should I see my doctor or asthma nurse again?

Your doctor or asthma nurse will probably want to see you within a month after you start using a preventer. They will be able to adjust your medicines if your symptoms are not decreasing. Or, if your preventer works well for you, you may be able to cut down on the number of puffs you take each day, or the strength of the medicine.

Do I really need to take my preventer every day?

Yes. To work properly, preventers need to be taken every day, usually morning and evening, even if you are feeling well. The protective effect of the preventer medicine builds up gradually.

Once this protection is working, occasionally forgetting to take your inhaler will usually not have bad effects. But forgetting or stopping for several days at a time will mean your protection begins to disappear. If you stop using your preventer, chest infections are more likely to bring on an asthma attack.

Will my preventer medicines change?

Yes. It is likely that you will have to change your medicines from time to time.

If your asthma gets really bad, you may need to increase the dose you take. Or you may need a short course of steroid tablets as well as your regular preventer.

When you begin taking preventer medicine, your doctor or asthma nurse may want you to take a higher dose each day. This will get your asthma under control quickly. As your symptoms improve, you may be able to take fewer daily puffs or move to a lower strength inhaler.