Epicutaneous allergen immunotherapy

IgE-mediated allergies have reached a high prevalence in industrialized countries and today represent a major socioeconomic burden. Allergen specific immunotherapy represents the only treatment that has a long lasting effect and can block progression of disease. However, patient compliance and treatment adherence to conventional subcutaneous allergen immunotherapy is poor and could not be improved with the introduction of SLIT. The main problems are adverse allergic side effects associated with allergen administrations as well as the long treatment duration. Therefore, it would be important to improve current immunotherapy protocols in terms of both safety and efficacy. The optimal route for allergen administration should be characterized by two hallmarks: i) absence of vascularization as to prevent accidental intravascular allergen administration and therefore systemic allergic side effects, thus improving safety. ii) A high density of antigen presenting cells, which should enhance the immune response to the administered allergen, allowing to reduce the number of required allergen administrations and therefore allowing to shorten treatment duration. Allergen administration into the epidermis is an interesting route in both respects. As a multilayered epithelium, the epidermis contains no vasculature. Also, the epidermis contains a high density of potent professional antigen presenting cells, i.e. Langerhans cells. This review focuses on the rationale, historical as well as recent clinical results of epicutaneous allergen specific immunotherapy, called EPIT.