A Warning About Phototherapy
If you're using any kind of phototherapy, including natural sunlight, you should always make sure that you're not being exposed to risky levels of ultraviolet rays. More isn't better, since sunburn can irritate your psoriasis. Too much sun can also increase you chances of developing cancer. Getting too much light is easier than you might think. For instance, if you're using UVB or PUVA, you shouldn't also sun yourself in the yard, or even go out for a walk without sunscreen. During treatment with artificial light, make sure to cover up areas of skin that don't require therapy with sunscreen or clothing.
Many medications, supplements, foods, and even perfumes can increase your sensitivity to light, including some high blood pressure drugs and antibiotics, St. John's wort, and even celery. Be careful to avoid these substances when you're receiving phototherapy. Also, if you're using phototherapy, especially PUVA, you should have regular skin exams to check for signs of skin cancer.
Finally, phototherapy often involves multiple visits to the doctor's office each week, which may make it hard to schedule.