Inhalers - relievers & preventers

One of the most widely used treatments for asthma is inhalers (also known as puffers). Inhalers contain a solution of medicine and a propellant which is used to create a fine spray that can be breathed in. Since this goes straight into the airways a much smaller dose of the drug is required than if it were taken in tablet or liquid form. The drug will treat the airways and lungs, only a small amount will get into the rest of the body (via the bloodstream) therefore resulting in fewer side-effects.

There are two types of inhaler:

  • Relievers
  • Preventers


Relievers help to relieve asthma symptoms when they happen, everyone with asthma should carry one. The medicine quickly relaxes the muscles around the narrowed airways which then allows the airways to open wider, therefore making it easier to breathe again. Generally, for people who only have symptoms every now and then the occasional use of a reliever inhaler may be all that is needed. However, if you need a reliever three times a week or more to ease symptoms, your asthma symptoms wake you up once a week or more or you have had an asthma attack in the last two years then having a preventer inhaler as well is usually advised.

There are several inhaler brands made by different companies. There are different inhaler devices that deliver the same reliever medicine. These inhalers are often (but not always) blue in colour. Other inhalers containing different medicines can be blue too. Always read the label and speak to your doctor to find out if this type of inhaler is suitable for you.


The drug used in preventer inhalers is a low dose of steroid called corticosteroids and they are not used to treat an asthma attack but help to control the swelling and inflammation in the airways, which will mean that the airways are less likely to become narrow and cause symptoms such as wheezing. For the protective effect to build up they need to be taken every day (usually morning and evening) to prevent symptoms from developing. If there is a flare-up of asthma symptoms, then it may be necessary to take the preventer inhaler more often. It will generally take 7-14 days for the steroid in a preventer inhaler to build up its effect. After this time the symptoms have often gone or are much reduced. It can, however, take up to six weeks for maximum benefit. It is important to continue taking these even when you are feeling well because it builds up your asthma protection over time. If you stop taking your preventer inhaler you will not get the full benefits and will be more likely to react to asthma triggers.

If asthma symptoms are well controlled with a regular preventer inhaler then there may not be a requirement to use a reliever inhaler very often. Preventer inhalers are usually brown, red or orange in colour.

There are several inhaler devices that will suit different people, and these are divided into four groups:

  • Metered dose inhalers (MDIs)
  • Breath-activated inhalers – MDIs and dry powder inhalers
  • Inhalers with spacer devices
  • Nebulisers

Standard MDI Inhaler

Asthma inhalersThis device is the most widely used inhaler and is used to deliver several types and brands of drugs. It uses a pressurised inactive gas that propels a dose of the drug in each ‘puff’. The dose is released by pressing the top of the inhaler. It is quick to use, small and convenient to carry but needs good co-ordination to press the canister and breathe in fully at the same time. It is important to remember to shake the inhaler before using it, not to inhale too sharply or at the wrong time and to hold your breath long enough after breathing in the contents.

Breath-activated Inhalers

These are alternatives to the standard MDI, some are still pressurised MDIs, but don’t require you to press the canister on top.

Other breath-activated inhalers are called dry powder inhalers. They do not contain the pressurised inactive gas that propels the drug and therefore you don’t have to push the canister to release a dose. Instead a dose is triggered by breathing in at the mouthpiece. To get the powder into the lungs you are required to breathe in hard.

Spacer Devices

These are used in conjunction with pressurised MDIs. They are a large plastic or metal container, with a mouthpiece at one end and a hole for the MDI at the other. The spacer between the inhaler and the mouth holds the drug when the inhaler is pressed. A valve at the mouth end ensures the drug is kept within the spacer until you breathe in. When you breathe out the valve will close. Since less coordination is required for a spacer these can be beneficial for children. In addition, a facemask can be fitted onto some types of spacers, instead of a mouthpiece which is sometimes done for young children and babies who can then use the inhaler simply by breathing in and out normally through the mask.


A nebuliser is a machine that creates a mist of medicine from the liquid form. This is then breathed in with a facemask or mouthpiece. This is no more effective than a normal inhaler but is useful for people who are tired with their breathing or are very breathless. They are used mainly in hospital or doctor’s surgeries for severe attacks of asthma when large doses of inhaled drugs are required.

For more information about inhalers talk to your doctor who can provide you with advice. Since there are lots of different coloured inhalers it is important to remember the name and colour of your device in case you need to see a doctor who does not have access to your medical records (i.e. in A&E, on holiday).

Sources used in writing this article are available on request

Information contained in this Articles page has been written by talkhealth based on available medical evidence. Our evidence-based articles are certified by the Information Standard and our sources are available on request. The content is not, though, written by medical professionals and should never be considered a substitute for medical advice. You should always seek medical advice before changing your treatment routine. talkhealth does not endorse any specific products, brands, or treatments.

Information written by the talkhealth team

Last revised: 18 March 2018

Next review: 18 March 2021