Sublingual Immunotherapy Not Currently Recommended For Asthma Control

Rebecca Normansell MA MB BChir Cochrane Airways Population Health Research Institute St George’s, University of London Interview with:
Rebecca Normansell MA MB BChir
Cochrane Airways
Population Health Research Institute
St George’s, University of London



Medical Research: What is the background for this study?

Response: Asthma is a common, long-term, respiratory condition which affects over 300 million people worldwide. It is a burden not only for the individual with asthma but also for the health services that care for them and the wider economy, due to days lost from work and school.

Asthma therapies aim to prevent attacks and improve symptoms by reducing airway constriction and inflammation, but they come with their own risks of side effects. For example, long-term high-dose inhaled corticosteroids have been associated with growth restriction in children and long-acting beta2-agonists as mono-therapy have been associated with increased risk of death in people with asthma.

There is growing interest in developing novel treatments for asthma and one such treatment is specific allergen immunotherapy. Immunotherapy has the potential to be a useful approach for asthma as it is thought that for approximately half of people with asthma, allergies are an important trigger for their symptoms and attacks. Immunotherapy can be delivered by injection (subcutaneously) or under the tongue (sublingually) and aims to bring about immune tolerance.

Immunotherapy has already been demonstrated to be effective in certain conditions, such as allergic rhinitis and wasp and bee sting allergy, but its effectiveness and safety in asthma is less clear. In fact, immunotherapy is not recommended at all for use in people with severe or uncontrolled asthma due to the risk of triggering a serious respiratory reaction.

Medical Research: What are the main findings?

Response: Our review looked for trials in which people with asthma who were given sublingual immunotherapy (SLIT) were compared with those given placebo, or who continued usual asthma care. We found 52 randomised controlled trials which met our inclusion criteria, allocating over 5,000 people to either SLIT or placebo/usual care. Most of the participants had mild asthma and were allergic to either house dust mite or pollen.

Despite the large number of eligible trials we were only able to perform a limited meta-analysis. This is because most of the trials did not report the efficacy outcomes we were most interested in: exacerbations and quality of life. Asthma symptoms and medication use were both more frequently reported, but often using different, un-validated scales so we did not perform a meta-analysis for these outcomes.

However, we were able to combine serious adverse event data from 22 trials involving 2560 participants and data for all adverse events from 19 trials including 1755 participants. SLIT did not appear to be associated with an increased risk of serious adverse events, although very few events were observed overall. SLIT was associated with a small increase in the risk of all adverse events, which in absolute terms equated to an increase from 222 per 1000 people in the control group to 327 per 1000 (95% confidence intervals 257 to 404). Importantly, many of these events were mild and transient local reactions and did not generally result in participants withdrawing from the trial.

Medical Research: What should clinicians and patients take away from your report?

Response: Sublingual immunotherapy is not currently recommended for the treatment of asthma. This is partly due to a lack of convincing evidence about efficacy and, perhaps more importantly, due to safety concerns. Our review supports this position as we cannot draw any clear conclusions about how well SLIT works for asthma and we cannot be at all sure that what we found about serious adverse events would apply to those with more severe asthma. As a result, confidence in our findings is generally low.

Medical Research: What recommendations do you have for future research as a result of this study?

Response: The global burden of asthma makes the quest for new, safe treatments a priority. SLIT has the potential to be a useful tool in asthma treatment. However, our review is limited by the infrequent reporting of exacerbations and quality of life, both of which are important outcomes for patients and policy makers. The use of varied, un-validated symptom and medication scores also meant we could not sensibly combine results in a meta-analysis. In the future, it would be helpful for trialists to use standardised, validated scales wherever possible and to report important events, such as exacerbations, even if they are very rare.


Cochrane Library (  Normansell R, Kew KM, Bridgman AL. Sublingual immunotherapy for asthma. Cochrane Database of Systematic Reviews 2015, Issue 8. Art. No.: CD011293. DOI: 10.1002/14651858.CD011293.pub2. is not a forum for the exchange of personal medical information, advice or the promotion of self-destructive behavior (e.g., eating disorders, suicide). While you may freely discuss your troubles, you should not look to the Website for information or advice on such topics. Instead, we recommend that you talk in person with a trusted medical professional.

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