Ultraviolet Light Therapy
Ultraviolet (UV) light causes profound biological changes, including temporary suppression of epidermal basal cell division followed by a later increase in cell turnover, and UV light-induced immune suppression. As a result, such skin conditions as psoriasis, mycosis fungoides, atopic dermatitis, and uremic pruritus may respond to therapy that uses timed exposure to UV light rays.
Emitted by the sun, the UV spectrum is subdivided into three bands—A, B, and C—each of which affects the skin differently. Ultraviolet A (UVA) radiation (with a relatively long wavelength of 320 to 400 nm) rapidly darkens preformed melanin pigment, may augment ultraviolet B (UVB) in causing sunburn and skin aging, and may induce phototoxicity in the presence of some drugs. UVB radiation (with a wavelength of 280 to 320 nm) causes sunburn and erythema. Ultraviolet C (UVC) radiation (with a wavelength of 200 to 280 nm) normally is absorbed by the earth’s ozone layer and doesn’t reach the ground. However, UVC kills bacteria and is used in operating-room germicidal lamps.
The drug methoxsalen, a psoralen agent, creates artificial sensitivity to UVA by binding with the deoxyribonucleic acid in epidermal basal cells. When administered before UVA light treatment, it photosensitizes the skin to enhance UVA’s therapeutic effect in a treatment called psoralen plus UVA (PUVA) therapy, or photochemotherapy. Other drugs used in combination with PUVA therapy include acitretin (Soriatane), an oral vitamin A derivative, and methotrexate.
Comparing Skin Types
| Skin ty | Sunburn and Tanning History |
|---|---|
| I | Always burns; never tans; sensitive (“Celtic” skin) |
| II | Burns easily; tans minimally |
| III | Burns moderately; tans gradually to light brown (average Caucasian skin) |
| IV | Burns minimally; always tans well to moderately brown (olive skin) |
| V | Rarely burns; tans profusely to dark (brown skin) |
| VI | Never burns; deeply pigmented; not sensitive (black skin) |
Contraindications to PUVA and UVB therapy include a history of photosensitivity diseases, skin cancer, arsenic ingestion, or cataracts or cataract surgery; current use of photosensitivity-inducing drugs; and previous skin irradiation (which can induce skin cancer). Ultraviolet light therapy is also contraindicated in patients who have undergone previous ionizing chemotherapy and patients who are using photosensitizing or immunosuppressant drugs. PUVA is also contraindicated in pregnant women.
Equipment
For Uva Radiation
Fluorescent black-light lamp ▪ high-intensity UVA fluorescent bulbs.
For Uvb Radiation
Fluorescent sunlamp or hot quartz lamp ▪ sunlamp bulbs.
For All Uv Treatments
Oral or topical phototherapeutic medications if necessary ▪ body-sized light chamber or smaller light box ▪ dark, polarized goggles ▪ sunscreen if necessary ▪ hospital gown ▪ towels.
Preparation of Equipment
The patient can undergo UV light therapy in a health care facility, in a doctor’s office, or at home. Typically set into a reflective cabinet, the light source consists of a bank of high-intensity fluorescent bulbs. (At home, the patient may use a small fluorescent sunlamp.)
Verify the doctor’s orders to confirm the light treatment type and dose.1 For PUVA, the initial dose is based on the patient’s skin type and is increased according to the treatment protocol and as tolerated. (See Comparing skin types.)
Implementation
Confirm the patient’s identity using at least two patient identifiers according to your facility’s policy.1
Inform the patient that UV light treatments produce a mild sunburn that will help reduce or resolve skin lesions.
Review the patient’s health history for contraindications to UV light therapy. Also ask whether he’s currently taking photosensitizing drugs, such as anticonvulsants, certain antihypertensives, phenothiazines, salicylates, sulfonamides, tetracyclines, tretinoin, and various cancer drugs.
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