Cochrane authors based at Cochrane Airways in St George’s University of London and the Cochrane CET have updated a review on Sublingual immunotherapy for asthma. Adding 14 new studies to give a total of 66 studies, they bring the review up-to-date. Unfortunately, even though there were a large number of people involved in the trial -  nearly 8000 - the review team were unable to draw firm conclusions.

Review question

The review assessed the evidence on the use of sublingual immunotherapy (SLIT) for people with asthma compared with placebo (dummy treatment) or with standard asthma care. The review focused on whether SLIT is a good treatment for asthma and whether it is safe.

Background

Asthma is a long‐term condition that causes breathing problems and cough, which sometimes develop into asthma attacks. This may lead to the need for patients to take extra medication, visit a clinic or a hospital for treatment, or even be admitted to the hospital. Approximately 300 million people worldwide have asthma, and allergies may be an important trigger of asthma symptoms in about half of these people (e.g. house dust mites, pollen). The aim of SLIT is to reduce the body's allergic response that causes asthma symptoms, which is done by giving repeated doses of what the person is allergic to in liquid or tablet form under the tongue. It is currently unclear whether SLIT is more helpful or safer for people with asthma, when compared with placebo or just continuation of normal asthma treatments.

Key points

• Review 66 studies involving 7944 people
• The included studies lasted between one day and three years, and most people in the studies had mild asthma. Both males and females were included, and about half of the studies included only children
• Most studies involved people with house dust mites or pollen allergy
• The review is current to 29 October 2019
• Very few included studies recorded the number of people who had asthma attacks (exacerbations) leading to a hospital visit or the need for additional medication, possibly because most people in the studies had mild asthma, so it was difficult to tell if they can be reduced by SLIT
• A few studies reported quality of life, but they used different scales, so it was unclear if SLIT had a positive effect
• Some studies reported that people taking SLIT had fewer asthma symptoms and a reduced need for asthma medication compared with the control group, but studies measured this information in lots of different ways so that it was difficult to combine or assess for accuracy
• People receiving SLIT were no more or less likely to experience serious unwanted side effects, but these were generally very rare. We are not confident that this finding would apply to people with more severe asthma
• People receiving SLIT were more likely to experience any unwanted side effect, but many of these were mild
• The evidence presented in this review is generally of moderate or low certainty

Conclusions

Despite continued study in the field, the evidence for important outcomes such as exacerbations and quality of life remains too limited to draw clinically useful conclusions about the efficacy of SLIT for people with asthma.
Review findings suggest that SLIT may be a safe option for people with well‐controlled mild‐to‐moderate asthma and rhinitis who are likely to be at low risk of serious harm, but the role of SLIT for people with uncontrolled asthma requires further evaluation.

This summary is based on the abstract and plain language summary. To find out about the search and other methods, and to read the full review, click here.