Non-Targeted UV Phototherapy

Non-targeted UV phototherapy affects healthy and unhealthy skin alike, and so must be applied at low dosages over many treatments.

Non-targeted” refers to administration of UV light, typically via a bulb resembling a fluorescent tube, to healthy skin as well as to affected skin. The UV bulbs radiate light in both the UVA and UVB spectrum, in either the UVA or UVB spectrum, or in what is termed Narrow Band UVB (NB-UVB = 300nm to 320nm). In some cases, the bulbs are arranged in a tall booth-like structure which the patient stands in while being irradiated by the bulbs. In other devices, a smaller bulb is inserted into a handheld wand and waved or held over the skin near the affected skin region.

Both modalities, the booth and handheld devices, irradiate healthy and unhealthy skin alike with UV light. For this reason, healthcare providers only administer enough UV light to be therapeutic but not enough to cause erythema of the healthy skin. Because the UV light administered is below the threshold required to cause erythema, the UV dosage is commonly referred to as Sub-Erythemic-Dosage, or SED. Prior to UV phototherapy, the minimal erythemic dosage (MED) for each patient is usually determined, and from there guidelines exist for determing what fraction of the MED will be administered to the patient for treatment.

Non-targeted UV phototherapy is very effective in the treatment of psoriasis, eczema, vitiligo, and other UV-treatable skin conditions. Non-targeted UV phototherapy is better suited than targeted UV phototherapy for disease covering more than 20% of the body. In many cases, targeted UV phototherapy can be used to treat the most troublesome portions of a patient’s disease first, followed by non-targeted UV phototherapy for the remaining parts of the disease and for maintenance. For psoriasis, non-targeted UV phototherapy typically requires between 32 and 40 treatments to produce “clearance” of a psoriatic lesion. There are different definitions of “clearance”, for example one definition is a reduction in a patient’s Psoriasis Area Severity Index (PASI) score of 75%. Treatments are administered between 2 and 3 times per week, over several months. Sunblocks or other barriers may be applied to healthy skin to reduce the effects of the non-targeted UV radiation there. Patients can obtain this treatment at their healthcare provider’s clinic and in some cases qualify for home therapy units allowing treatment in private.

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