In medicine, a Nebulizer^[1] or nebuliser^[2] (see spelling differences) is a drug delivery device used to administer medication in the form of a mist inhaled into the lungs. Nebulizers are commonly used for the treatment of cystic fibrosis, asthma, COPD and other respiratory diseases or disorders.

Analytical nebulizers are another form of nebulizer and are used primarily in laboratory settings for elemental analysis.

Nebulizers use oxygen, compressed air or ultrasonic power to break up solutions and suspensions into small aerosol droplets that can be directly inhaled from the mouthpiece of the device. An aerosol is a mixture of gas and solid or liquid particles.

Various asthma guidelines, such as the Global Initiative for Asthma Guidelines [GINA], the British Guidelines on the management of Asthma, The Canadian Pediatric Asthma Consensus Guidelines, and United States Guidelines for Diagnosis and Treatment of Asthma each recommend metered dose inhalers in place of nebulizer-delivered therapies.^[3] The European Respiratory Society acknowledge that although nebulizers are used in hospitals and at home they suggest much of this use may not be evidence-based.

Recent evidence show that nebulizers are no more effective than metered-dose inhalers (MDIs) with spacers.^[5] An MDI with a spacer may offer advantages to children who have acute asthma.^[3][6][5] Those findings refer specifically to the treatment of asthma and not to the efficacy of nebulisers generally, as for COPD for example.^[5]For COPD, especially when assessing exacerbations or lung attacks, there is no evidence to indicate that MDI (with a spacer) delivered medicine is more effective than administration of the same medicine with a nebulizer.^[7]

The European Respiratory Society highlighted a risk relating to droplet size reproducibility caused by selling nebulizer devices separately from nebulized solution. They found this practice could vary droplet size 10-fold or more by changing from an inefficient nebulizer system to a highly efficient one.^[4][8] Two advantages attributed to nebulizers, compared to MDIs with spacers (inhalers), were their ability to deliver larger dosages at a faster rate, especially in acute asthma; however, recent data suggests actual lung deposition rates are the same. In addition, another trial found that a MDI (with spacer) had a lower required dose for clinical result compared to a nebulizer (see Clark, et al. other references).^[3]