People who are allergic to cats may not have to get rid of their pets to find relief, if the findings of a new study hold up.

Tolerance to cats can be built up in allergic kids by placing increasing doses of standardised cat dander extract under the tongue, according to Spanish researchers.

In the medical journal Allergy, Dr Emilio Alvarez-Cuesta, of Hospital Ramon y Cajal, Madrid, and colleagues note that a first line step for people with cat allergy is to remove cats from the home. However, this is often rejected or is not entirely effective, leaving immunotherapy as the only treatment.

Immunotherapy is based on the idea that the immune system can “learn” to tolerate allergy triggers if it is exposed to gradually increasing amounts of the offending allergen, starting with tiny amounts that don’t cause an allergic reaction.

In sublingual immunotherapy, or SLIT, the allergen is placed under the tongue, where it is absorbed into the system.

To see whether SLIT using cat dander extract works for cat allergies, the researchers randomly assigned 50 allergic youngsters to get daily SLIT drops with increasing levels of cat allergen or inactive “placebo” drops for a year.

The participants were then “challenged” by spending up to 90 minutes exposed to allergens in a room in which a cat was housed.

Of the 33 participants who completed the SLIT course, 62 per cent showed a marked reduction in symptoms compared to their symptoms before treatment. They also showed improved peak expiratory flow values during exposure, and a reduction in skin test reactions to standardised cat extract. No significant changes were seen in the group that got placebo drops.

There were no reports of adverse reactions, and the investigators conclude the results suggest “that the cat SLIT used in this study was able to improve cat allergy based on natural exposure challenge”.