Abstract: A photoadjuvant immunotherapeutical method includes the steps of providing a phototherapeutical apparatus, comprising a light source, an optical guidance system, and a patient interface; determining a minimal erythema dose; performing phototherapy by irradiating a target surface with the phototherapeutical apparatus; and performing immunotherapy by exposing the irradiated target surface to an antigen. The method can be applied to treat allergic diseases, including allergic rhinitis, rhinoconjunctivitis, asthma, and atopic dermatitis, as well as to treat autoimmune diseases. UVA, UVB and visible light can be used, emitted from a quartz bulb with a small discharge volume. The phototherapy increases the tolerance of a patient's body toward an antigen. During immunotherapy the irradiated target surface can be exposed to a naturally present antigen or to an administered antigen.