tion. Dermatologists recommend people who are
photosensitive:
- wear clothing that covers the arms, legs, head,
face, and neck when going outdoors, even
when the day is cloudy - liberally apply sunscreen at least 30 minutes
before going outdoors (many dermatologists
recommend applying sunscreen after getting
out of the shower in the morning so the skin
can absorb it) and frequently while outdoors - avoid exposure during the sun’s most intense
periods, typically between 10 a.m. and 4 p.m.
in most regions of the United States
See also ANTIBIOTIC MEDICATIONS; PHOTOPHOBIA;
PORPHYRIA.
phototherapy Treatment with ultraviolet light,
which suppresses the action of immune cells in
the SKIN(T-CELLS). Ultraviolet light also slows the
growth rate of keratinocytes, the cells that make
up much of the dermis and nearly all of the epi-
dermis, helping reduce symptoms such as plaque
formation and scaling. Phototherapy is effective
for numerous chronic dermatologic conditions,
notably PSORIASIS, VITILIGO, and atopic DERMATITIS.
Many people require therapeutic phototherapy to
bring symptoms under control, with ongoing
maintenance treatments to help prevent recurrent
outbreaks or to continue subduing the IMMUNE
RESPONSE. With appropriate protection to prevent
ultraviolet damage to the eyes and skin, pho-
totherapy has few short-term side effects. Ques-
tions remain, however, about long-term
consequences such as the same problems that
accompany extended sun exposure (notably SKIN
CANCER). Dermatologists use three types of pho-
totherapy: ultraviolet B (UVB) phototherapy, pso-
ralen plus ultraviolet A (PUVA) phototherapy, and
excimer laser phototherapy.
UVB phototherapy UVB lightwaves are less
intense than ultraviolet A (UVA) lightwaves,
achieving a therapeutic benefit with low risk of
sunburn and other complications. UVB photother-
apy was the first therapeutic application of ultravi-
olet light and remains the most common one in
use today. Dermatologists use two forms of UVB
phototherapy: broadband, the conventional UVB
phototherapy, and narrowband, which employs a
narrower width of ultraviolet light. Narrowband
UVB phototherapy is often more effective for
treating psoriasis, though has a higher risk of sun-
burn than broadband UVB phototherapy. For UVB
phototherapy treatments, the person stands inside
a small room called a light box with the areas of
skin exposed that are to receive treatment. Other
skin surfaces remain clothed or covered, though
treatment may be appropriate for nearly the entire
body.
PUVA phototherapyPUVA lightwaves provides
a stronger, more focused therapeutic effect. UVA
lightwaves are more intense than UVB lightwaves.
Psoralen is a photosensitive substance taken orally
as a pill or applied as a lotion to lesions and
desired skin surfaces. Short exposures to UVA
lightwaves activate the psoralen, which intensifies
the effect. This combination reduces the risk for
complications such as sunburn during treatment.
However, the skin remains photosensitive for up
to 36 hours after treatment, requiring the person
to avoid all sun exposure for 12 to 36 hours fol-
lowing a PUVA phototherapy session. The individ-
ual must also wear sunglasses after taking oral
psoralen because the psoralen tends to accumulate
in the retinal tissues of the eyes. Some people
have an ADVERSE REACTIONto psoralen including
NAUSEA, vomiting, itching (PRURITUS), and height-
ened sensitivity to sun exposure even after PUVA
phototherapy ends.
Excimer laser phototherapy Another type of
phototherapy is the excimer laser, which emits
high-intensity UVB lightwaves that the dermatol-
ogist focuses on specific lesions or defined areas of
the skin’s surface. Such laser phototherapy allows
targeted treatment and limits the risk for sunburn,
though targeted lesions often acquire deeper pig-
mentation than the surrounding skin and may
SCARafter HEALING. Often the hyperpigmentation
fades over time. Dermatologists generally reserve
excimer laser phototherapy for conditions that do
not respond to other treatments.
See alsoKERATINOCYTE; LESION; NEONATAL JAUNDICE.piercings Skin piercings for cosmetic purposes
have become popular in the United States, espe-
cially among young people. Most people who
have piercings experience minor complications at184 The Integumentary System