Light and Vitamin D UVB exposure induces the production of
vitamin D in the skin. The majority of positive health effects
relate to this vitamin which has regulatory roles in calcium
metabolism (which is vital for normal functioning of the nervous
system, as well as for bone growth and maintenance of bone
density) immunity, cell proliferation, insulin secretion and
blood pressure. "Narrowband" UVB has become the phototherapy
treatment of choice for psoriasis, vitiligo, atopic dermatitis
(eczema) and other photoresponsive skin disorders. Conventional
Broadband UVB lamps emit light in a broad range over the UVB
spectrum, including both the therapeutic wavelengths specific to
the treatment of skin diseases, plus the shorter wavelengths
responsible for sunburning (erythema). Sunburning has a negative
therapeutic benefit, increases the risk of skin cancer, causes
patient discomfort, and limits the amount of therapeutic UVB
that can be taken. "Narrowband" UVB lamps, on the other hand,
emit light over a very short r