Before you undertake a treatment
program with phototherapy it is important to understand
how your skin will react to the light. Also, you must
let your doctor know if you have any other health problems
and what other medications you are on. Some health problems
may prohibit you from receiving phototherapy (contraindications).
Your doctor could decide you should not be treated with
phototherapy for one of the following reasons:
You have another disease that
causes your skin to be very sensitive to UV light (e.g.,
systemic lupus
erythematosus, polymorphic light
eruption).
The medication(s) you take for
your other medical conditions make your skin more sensitive
to UV.
You have a past history of melanoma
(the most serious form of skin cancer of the pigment-
producing cells in the skin, called
melanocytes).
Your doctor could also decide
to avoid phototherapy if you have a history of another
type of skin cancer (such as squamous cell carcinoma
or basal cell carcinoma); those with such a history
are at a greater risk for developing new skin cancers
when exposing themselves to the sun or artificial light
sources, such as those used in phototherapy.
Phototherapy can increase the
risk of skin cancer, particularly if used over long
periods. If you are having regular phototherapy treatment
for your psoriasis, you should also plan for regular
skin examinations to be sure no such skin cancers have
developed. In addition, if at any time you recognize
any non-healing areas on your skin or new growths of
concern, arrange to see your doctor. Excess UVL, especially
PUVA, will accelerate the appearance of photo-aging
of the skin.
Studies have shown that psoralen
plus ultraviolet A (PUVA) light treatment has been linked
to the most serious form of skin cancer, cutaneous melanoma.
However, this is rare and generally happens only when
PUVA treatment is given over a prolonged period.
Prior to beginning treatment with
UV light, your doctor will start therapy based on your
skin type. Dr. Thomas Fitzpatrick defined skin type
based on the skin's response to sunlight exposure. This
method groups skin types from I to VI based on whether
the skin burns or tans in response to sunlight exposure.
This guideline is one method used to determine the starting
dosage of ultraviolet therapy.
A second method your doctor
may use to determine your starting dose of ultraviolet
radiation is through skin testing. This involves exposing
small areas of skin sequentially to different intensities
of ultraviolet B radiation to see the response of your
skin.
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