ALTERED IMMUNE RESPONSE ALLERGIC REACTIONS When the antigen is environmental or exogenous and triggers the immune process, it is called an allergy. The antigen that initiates the immune process is called an allergen. Type: There are two types of allergic reactions; Atopic and non-atopic disorders. In atopic disorders there is an inherited local reaction to IgE and the production of antibodies. For example: allergic rhinitis, asthma and atopic dermatitis. Non