Topical lesions can be significantly reduced due to regular sunlight doses. Light therapy is considered effective and therefore was frequently recommended by doctors as treatment for psoriasis, especially in persistent, complicated cases. Though PUVA comprising a combination of drug psoralen with ultraviolet A light (UVA) was often chosen as a method in recent years its application is decreasing nowadays because of its potential possibility to cause skin cancer even years after being used.
Alternatively, ultraviolet B (i.e. UVB) light treatment can be prescribed by some doctors. The method implies applying a light box only or combined with other means, for example coal tar. Being as effective as PUVA method this technique, known as UVB narrow-band therapy, is not so carcinogenic.