The present disclosure is directed to systems and methods for targeted UVB phototherapy for treating autoimmune disorders and other indications. In one embodiment, a phototherapeutic system can include a radiation source configured to emit light. At least 75% of the light emitted by the radiation source can have a target wavelength range with a bandwidth between 298 nm and 307 nm. The phototherapeutic system can also include a controller operably connected to the radiation source and configured to deteirnine a dosage for a phototherapy session. Dosage can correspond to a product of the intensity of the radiation source and an exposure time of the radiation source, and may have an upper bound less than 1 minimal erythema dose (MED). Delivery of the dose of phototherapy can stimulate an immune response to treat an autoimmune disorder.
