SLIT, or sublingual immunotherapy, delivers small amounts of specific allergens to the patient in drops it tablets which dissolve under the tongue prior to the onset of the allergy season with the aim of gradually accustoming or desensitising the immune system to that allergen so that when it meets if for real it does not react.
Italian researchers, led by Dr. Gabriele Di Lorenzo of the University of Palermo, have now combined the results of 19 clinical trials (lasting from three months to three years) conducted since 1995 on the effectiveness of immunotherapy tablets and drops against hay fever caused by grass pollen.
Across the studies, which included a total of 2,971 adults and children with grass-pollen allergies, immunotherapy reduced symptoms by about 20–30% on average, and allowed patients to reduce their use of antihistamines and other medications. The treatment appeared to be highly effective for many, but not all. patients. The researchers said that more work is needed to identify which patients might be most likely to benefit.
Dr Harold Nelson, an allergist at National Jewish Health in Denver, However, noted that while antihistamines reduce symptoms by about 12–15%, on average and nasal steroids appear to cut symptoms by about 17%, allergy shots appear to outperform the sublingual versions, with a symptom reduction about twice that of sublingual immunotherapy. Moreover, the long-term effectiveness of the grass-pollen tablets is not yet fully clear.
However, Dr Nelson said that if sublingual products do win approval in the US, they will likely boost the number of hay fever sufferers who want to use under-the-tongue immunotherapy as, ‘even though the effectiveness is less than that of allergy shots, the convenience of an at-home version of immunotherapy is a plus, and the sublingual therapy tends to have fewer side effects than shots’.
Journal of Allergy and Clinical Immunology, online August 5, 2010.
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First Published in August 2010
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