Narrowband UVB light therapy is available in an office-based light box, handheld XTRAC laser, as well as in hand and foot units. Narrowband UVB is felt to be much safer than light obtained in a tanning salon. For those patients with greater body surface area involvement and those with guttate psoriasis, narrowband UVB is extraordinarily effective in producing clearance in up to 75% of people. Risks include burning, photoaging, and potentially increased risk of non-melanoma skin cancer. Also, the treatments must be done 2 to 3 times a week for a minimum of 10 weeks, and then require ongoing maintenance therapy approximately once a week indefinitely. Some patients who respond well to narrowband UVB qualify for a home therapy unit.