Why is it that frequent exposure to an allergen can increase sensitivity and cause allergic reaction, yet repeated exposure to an allergen in allergy shots helps build ups immunity?
Regularly scheduled, repeated exposure to small amounts of an allergen can lead to immunity, whereas infrequent and erratic exposure does not confer immunity but increases the likelihood of producing allergen sensitization. Irregular exposure to allergens can lead to the production of antibodies (called IgE-mediated antibodies). The presence of these antibodies, when exposed to an allergen can lead to an allergic reaction. In allergy shots or immunotherapy, the allergen exposure is closely regulated and given on a scheduled basis. Small amounts of allergens are given over a period of time to build up to maintenance doses. This leads to the production of blocking antibodies (called IgG antibodies) and a decrease in the level of allergic or IgE-mediated antibodies.
