Hi, thanks for the D2D. Phototherapy is an effective treatment for psoriasis and currently, narrow band UVB is the main UV therapy used. NBUVB is UVB in the 311 to 313nm wavelength. This wavelength is an efficienct wavelength for the treatment of psoriasis.
Natural sunlight has a very broad spectrum wavelength, so while it does carry the therapeutic wavelengths, it also has other wavelengths that can cause more burns and skin damage.
So overall, medical UV therapy is better than natural sunlight in treating psoriasis.
