In many cases, psoriasis responds well to sunlight. The affected parts should be frequently exposed to the sun. The daily use of a sunlamp or ultraviolet light is also beneficial. If light is used as treatment, however, small precautions should be taken to avoid super-sensitivity of the skin to sun:
Avoid overdoses (more than 4000 IU per day) of vitamin D.
Do not eat celeriac, celery, or psoralea seeds on days you bathe in the sun.
Be aware that many prescription medications, especially those for high blood pressure, increase sensitivity to the sun.