Biologics target specific parts of the immune system that are overactive in psoriasis. They are used if you have moderate to severe psoriasis that has not responded to systemic treatments or if you cannot use other treatments. How often you take the biologic varies from every 2 weeks to once every 3 months depending on the biologic. They are usually given by injection, which can be given at home by yourself or, in the case of one biologic, in hospital through an infusion drip. There are a number of biologics available, and their availability differs widely from country to country; your doctor or healthcare provider will be able to discuss and select the most appropriate one for you.