Besonnung

Besonnung is a German term that refers to exposure to sunlight or ultraviolet radiation. In everyday language it denotes sun exposure for tanning or warmth, but in scientific and clinical contexts the word is used to describe controlled light exposure for therapeutic or agricultural purposes. The concept covers both human health applications and plant cultivation, with differences in goals, methods, and safety considerations.

In medicine and dermatology, Besonnung or Besonnungstherapie describes phototherapy using ultraviolet light to treat skin diseases such as psoriasis, eczema, or vitiligo. Treatments are typically conducted under medical supervision, with gradually increasing exposure and careful dosing. Common modalities include UV-B phototherapy and PUVA (psoralen plus UVA) or, in many settings, narrowband UV-B. Benefits can include symptom relief and enhanced vitamin D synthesis, while risks include erythema, burns, photoaging, and an increased long-term risk of skin cancer. Patients are monitored for tolerance and adverse effects, and protection of non-affected areas is maintained.

In horticulture and agriculture, Besonnung refers to the deliberate exposure of plants or seeds to light. It affects germination, growth, and flowering and is managed through control of photoperiod (length of light exposure), light intensity, and shading. In greenhouses, nurseries, or seedbeds, Besonnung schedules are used to synchronize development, strengthen plants, or influence flowering in certain species.

Etymologically, Besonnung combines the prefix be- with Sonne (sun) and is primarily used in German-speaking contexts. In English, the corresponding terms are usually “sun exposure” or “phototherapy,” depending on the application.

See also: Phototherapy, UV radiation, vitamin D synthesis, photoperiod, horticulture, plant photomorphogenesis.