As dermatologists, we recommend 20 minutes of sun exposure, three times a week on psoriasis patches without sunscreen. You want to put sunscreen on all your other normal skin, but on the psoriasis patches, you want to leave off sunscreen. UV light therapy reduces cell proliferation, and psoriasis is a disease where the skin is growing too fast. By getting that UV light, the skin will stop growing as quickly. If your psoriasis is detrimental to your quality of life, you should definitely see a dermatologist. These days, there are super effective treatment options for psoriasis.