1. What is Phototherapy?
Phototherapy is a branch of photomedicine in which various wavelengths of ultraviolet, visible, and infrared light are used for
therapeutic purposes. Below is an example of the Electromagnetic Spectrum to help show the different bands of ultraviolet light
that are used in phototherapy treatments for certain diseases of the skin.
Of the different bands of ultraviolet light, Narrowband UVB is the most common type of light used in phototherapy and has proven
to be the most beneficial component of ultraviolet light for the treatment of psoriasis and other skin disorders. The primary side effects
of phototherapy are erythema (sunburn) and the risk of premature aging of the skin. The treatment regimen consists of gradually
increased doses of ultraviolet light delivered to the patient’s skin. The doses are measured in millijoules per square centimeter (mj/cm2
)
and typically last several minutes.
Understanding Phototherapy
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A typical home phototherapy unit
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The Electromagnetic Spectrum
Vitiligo
With vitiligo, Narrowband UVB light penetrates the skin to reach melanocytes
resting in the niche of the hair follicle. Melanocytes are pigment producing cells.
Once the pigment producing cells are stimulated, how well lesions fill in will be
determined by the location on the body, duration of the disease, and the type
of vitiligo. Vitiligo patients typically require more treatments than
patients with psoriasis or atopic dermatitis.
Narrowband Broadband
Sunlight UVA (PUVA)
Ultraviolet Lamps vs Sunlight
Plaque Psoriasis
Epidermis
Capillary
Dermis
Psoriasis
280 300 320 340 360 380 400
10-13 10-11 10-9 10-7 10-5 10-3 10-1 10
Visible light
Wavelength Gamma rays X-rays Ultraviolet Infrared Microwaves Radio waves
100-280 nm 320-400 nm
280-320 nm
MIDDLE WAVE UV
(UV-B)
LONG WAVE UV
(UV-A)
SHORTWAVE UV
(UV-C)
Epidermis
Dermis
Capillary
A patient will likely require a course of 20-30 treatments over several
weeks to clear his or her skin. This clearance can then be maintained
with less frequent treatments.
Conditions Treated
with Phototherapy
Narrowband UVB is safe and effective for a variety
of skin diseases, especially Psoriasis and Vitiligo.
Other diseases include:
• Atopic Dermatitis (Eczema)
• Cutaneous T-Cell Lymphoma (Mycosis Fungoides)
• Chronic Ordinary Urticaria (Hives)
• Eosinophilic Pustular Folliculitis
• Pityriasis Rosea
• Mast Cell Disorders
Diseases that are commonly treated with PUVA include
Scleroderma / Morphea and Lichen Sclerosus.
Phototherapy Treatments
Narrowband UVB light penetrates into the upper layers of the skin and helps balance the immune
system cells linked to inflammation and excessive growth, which causes the symptoms of psoriasis.
In the majority of patients who respond well to phototherapy, the psoriasis patches will start to
become smaller and thinner within five to ten treatments.
Normal Skin
Normal skin after
phototherapy
UVA2 320-340 nm
UVB Narrowband 311-312 nm
UVA1 340-400 nm
Inflammatory cell infiltration
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