Allergen immunotherapy (AIT), also known as allergy shots or allergy desensitisation therapy, is a medical treatment aimed at reducing or eliminating allergic reactions to specific substances, known as allergens. It is primarily used to treat allergic rhinitis (hay fever), allergic asthma, and insect sting allergies.
Allergens are substances that trigger allergic reactions in susceptible individuals. Common allergens include pollen, dust mites, pet dander, mould spores, and certain foods.
Allergen immunotherapy works by gradually desensitising the immune system to specific allergens. The treatment involves administering regular injections or sublingual (under-the-tongue) drops of gradually increasing doses of the allergen extract over several months to years.
When a person with allergies is exposed to an allergen, their immune system overreacts, producing allergic symptoms such as sneezing, itching, congestion, or wheezing. Allergen immunotherapy works by exposing the immune system to small, controlled doses of the allergen, which helps the body build tolerance over time.
“This therapy is a century-old concept in the treatment of asthma. However, it is not considered as the sole treatment for asthma. It is an add-on treatment in selective cases, especially in asthma with allergic rhinitis,” said Dr Sujith Varghese Abraham, specialist pulmonologist, respiratory medicine, KIMS Health. As per the Real-time Assessment of Community Transmission study published in Lancet in 2021, AIT aided in stepping down asthma treatment and reduced controller and reliever prescriptions. A greater reduction in severe asthma exacerbation was also noted in AIT patients. AIT can be considered in any stage of asthma but pre-requisites have to be met.
“For individuals with asthma considering allergen immunotherapy, prerequisites include demonstrable allergy to specific allergens like house dust mites, concurrent rhinitis, and a lung capacity measured by forced expiratory volume (FEV1) greater than 70%. Additionally, those who exhibit insufficient responses to common anti-allergy medications or experience intolerable side effects may be considered candidates for AIT,” said Dr Sujith Varghese Abraham.
While allergen immunotherapy demonstrates efficacy in addressing allergies triggered by airborne allergens like pollen, dust mites, and pet dander, its effectiveness in managing food allergies may be limited.