A review of 88 studies on allergens since 2001 has found that allergy shots or allergen immunotherapy can reduce asthma symptoms or attacks.

The review appearing in the current issue of The Cochrane Library stated that asthma patients covered by the studies improved their breathing after receiving allergy shots that desensitised the immune system from specific irritants.

Dr. Michael Abramson, a pulmonologist at the Monash University in Melbourne, Australia and co-author of the review, said doctors should consider immunotherapy for appropriate asthma patients.

The review authors also said that allergy drops placed under the tongue may also be effective asthma control with minimal serious side effects.

However, Dr. Harold Nelson of the National Jewish Health in Denver, Colorado cautioned that people with treatment-resistant asthma are not candidates for allergy shots.

A 30-minute or 45-minute observation after the allergy shots should be done so that any serious side effects could be easily treated.