How do inhalers work?

Inhalers are the main way medicines are delivered directly into the lungs. They are most commonly used to treat conditions such as asthma and chronic obstructive pulmonary disease (COPD), where the airways become narrowed or inflamed, making breathing difficult.

Because inhaled medicine goes straight to the lungs, only a small dose is needed compared with tablets or liquid medicines. This usually means fewer side effects and faster relief, provided the inhaler is used correctly.

What does an inhaler do?

An inhaler delivers medicine directly into your airways and lungs. The aim is to reduce symptoms such as wheezing, breathlessness, chest tightness, and coughing by either opening the airways or reducing swelling (inflammation) inside them.

Different inhalers contain different medicines, and they are used for different purposes depending on how often symptoms occur and how severe they are.

How do inhalers work inside the lungs?

Inhalers work by targeting the airways (bronchi), which can become narrow and inflamed in conditions such as asthma and COPD. The medicine acts locally, meaning it works where it is needed most.

Reliever inhalers

Reliever inhalers work quickly to relax the muscles around your airways, helping them open up. This makes breathing easier within minutes.

They are used when symptoms occur, such as sudden breathlessness, wheezing, or during exercise or a chest infection. Their effects usually last for a few hours.

Common examples include salbutamol (for example Ventolin®) and terbutaline (for example Bricanyl®). These are often blue inhalers.

Preventer inhalers

Preventer inhalers work more slowly but are essential for long-term control. They reduce inflammation inside the airways, making them less sensitive and less likely to react to triggers such as allergens, cold air, or exercise.

They need to be taken every day, even when you feel well. Over time, they help reduce symptoms, improve lung function, and lower your risk of severe asthma attacks or COPD flare-ups.

Most preventer inhalers contain a low dose of corticosteroid medicine.

Combination inhalers

Combination inhalers contain two medicines in one device. A preventer - usually a steroid - and a long-acting reliever (bronchodilator). The preventer reduces inflammation, while the long-acting medicine helps keep your airways open for longer periods.

These are often used when symptoms are not fully controlled with a preventer alone.

How quickly do inhalers work?

The speed at which an inhaler works depends on the type of medicine it contains.

Blue reliever inhalers

Blue reliever inhalers usually start working within minutes. They are designed for quick relief of symptoms such as wheezing and breathlessness. However, their effects typically wear off after a few hours, so they do not provide long-term control.

Steroid preventer inhalers

Steroid preventer inhalers do not provide immediate relief. They build up their effect over days to weeks of regular use. With consistent use, they reduce inflammation in your airways and help prevent symptoms from developing in the first place.

Do all inhalers work in the same way?

No. Inhalers can look similar but work in different ways depending on how the medicine is delivered into the lungs.

Metered-dose inhalers

Metered-dose inhalers (MDIs) release a measured puff of medicine when the canister is pressed. They require good coordination between pressing the inhaler and breathing in.

If used incorrectly, much of the medicine can end up in your mouth and throat rather than your lungs.

Dry powder inhalers

Dry powder inhalers (DPIs) release medicine as a fine powder. These do not require you to press a canister at the same time as inhaling, but they do require a strong, fast breath in to draw the medicine into your lungs.

Breath-actuated inhalers

Breath-actuated inhalers automatically release a dose when you start to inhale. These can be helpful for people who struggle with coordination using standard inhalers.

Spacers

A spacer is a plastic chamber attached to a metered-dose inhaler. The medicine is sprayed into the spacer first, and then inhaled slowly and deeply.

Spacers make it easier to use inhalers correctly and improve how much medicine reaches your lungs, while also reducing side effects such as throat irritation.

What happens if an inhaler isn't used correctly?

If an inhaler is not used correctly, much of the medicine may not reach your lungs. Instead, it may stay in your mouth or throat, where it is far less effective and may cause side effects.

With metered-dose inhalers, common mistakes include pressing too early or too late during inhalation, which reduces the amount of medicine delivered to your lungs.

Using a spacer can significantly improve delivery, particularly for reliever inhalers. Healthcare professionals, including GPs and pharmacists, can check inhaler technique and help correct any issues.

Can your inhaler stop working?

Summary

Inhalers deliver medicine directly into your lungs to treat and prevent conditions such as asthma and COPD. Reliever inhalers work quickly to ease symptoms, while preventer inhalers reduce inflammation over time to help prevent symptoms.

Different inhaler types require different techniques, and using them correctly is essential for them to work properly. If symptoms are not well controlled you should speak to a healthcare professional.