Allergic diseases such as allergic rhinitis (nasal allergy), allergic conjunctivitis (ocular allergy) and asthma are chronic diseases. These diseases are caused by the immune system reacting inappropriately to normally harmless substances such as pollens, dust mites, mold spores and animal dander. While there are drugs such as steroids and antihistamines that can effectively control the symptoms, one of the options for eliminating the root cause of the problem is allergen immunotherapy (also called desensitization, hyposensitization or allergy shots).
Allergen extracts are prepared according to the sensitivities of the individual. The extracts are administered at regular intervals to induce a response called immune tolerance. The tolerance response is achieved by the development of blocking antibodies and regulatory T cells. When this happens, the patient’s sensitivity to the allergens progressively declines, and clinical symptoms diminish. Studies have shown that after three to five years of treatment, the effectiveness persists long-term even after treatment is discontinued.
Allergic rhinitis in childhood is a risk factor for the development of asthma. Studies have shown that children who received 3 years of allergen immunotherapy for allergic rhinitis were 2.5-fold less likely to become asthmatic. This effect was still evident 7 years after completing treatment.
Studies have also shown that for a subset of patients with atopic dermatitis, where environmental allergy is a major factor in their illness, immunotherapy is effective in reducing the severity of their skin disease.
Allergen immunotherapy has traditionally been administered by subcutaneous injections. Newer forms of treatment such as sublingual immunotherapy have been developed that are more convenient, and maybe suitable for selected patients.