Psoriasis Treatment: UV Phototherapy
UV Phototherapy comes in two forms: Non-Targeted and Targeted.
Ultraviolet (UV) light is a natural part of all sunlight.
UVA light (320 to 400nm) and UVB light (280 to 320nm) are the UV radiation wavelengths which reach the surface of the earth. It is generally known that exposure to too much sunlight, specifically too much UVA and UVB light, causes sunburn, aging of the skin, and in some cases, skin cancer. That is why sunblocks try to keep UVA and UVB light from reaching the skin they are applied to. It is less generally known that sunlight strongly affects the immune system of the skin in beneficial ways for patients with psoriasis, eczema, vitiligo, and various other skin conditions. One common characteristic of over-exposure to the UV radiation of the sun (sunburn) is a reddening of the skin called “erythema”, caused by an increase in capillary blood supply called “hyperemia”. Hyperemia from UV radiation should not be confused as the source of color of psoriatic red patches which is typically caused by histamines released through immune system activity causing capillaries there to dilate and proliferate.
In summary, UV light interrupts the cycle of immune system activity which creates the psoriatic lesion, and UVB light in particular can destroy abnormally proliferating skin cells.
UVA and UVB light act in many ways to suppress the activity of the immune system of the skin. UVB light also has enough energy to induce “apoptosis”, or cell death of the skin cells. The application of UVA and UVB light as an effective treatment of psoriasis has a long and very well studied history. UV phototherapy is considered less toxic than systemic and biologic drug therapy. In some cases, medicated topical products are combined with UV phototherapy as an effective therapy.
Some systemic and biologic drugs have been utilized in conjunction with UV phototherapy to:
- Improve therapeutic benefit, the two treatments working together better than either alone
- To achieve the same therapeutic benefit as the drug alone, while being able to reduce the drug dosage which reduces the toxic damage the systemic and biologic drugs cause in the patient
There are several types of UV phototherapy devices. Treatment is issued in one of two ways: non-targeted and targeted. Non-targeted refers to delivering lower dosage UV light to healthy and psoriatic skin alike, two to three times per week, over several months. Targeted phototherapy refers to delivering higher dosages of UV light to only psoriatic skin, sparing healthy skin, twice per week over 3 to 5 weeks.