PUVA Therapy - Procedure

Procedure

Psoralens are photosensitizing agents found in plants. Psoralens are taken systemically or can be applied directly to the skin. The psoralens allow a relatively lower dose of UVA to be used. When they are combined with exposure to UVA in PUVA, they are highly effective at clearing psoriasis. Like UVB light treatments, the reason remains unclear, though investigators speculate there may be similar effects on cell turnover and the skin's immune response.

Choosing the proper dose for PUVA is similar to the procedure followed with UVB. The physician can choose a dose based on the patient's skin type. Often, however, a small area of the patient's skin will be exposed to UVA after ingestion of psoralen. The dose of UVA that produces uniform redness 72 hours later, called the minimum phototoxic dose (MPD), becomes the starting dose for treatment.

At the very least for vitiligo, narrowband ultraviolet B (UVB) phototherapy is now used more commonly than PUVA as it is less damaging to the skin. As with PUVA, treatment is carried out twice weekly in a clinic or every day at home, and there is no need to use psoralen.