The phototherapy of vitiligo Biological effects of light on the skin; UVA and UVB generators; photosensitizing agents. UV-ray phototherapy is one of the best methods for the treatment of vitiligo. A most common therapy was based on the use of UVA generators irradiating the whole exposed skin surface. This kind of phototherapy had unfavourable consequences: first, the vitiligo patch reacted to the light stimulus with a simple reddening, often intense but short lasting, since UVA rays are not able to promote the production of new melanin. At the same time, the normally pigmented surrounding skin became lastingly tanned, so that the colour difference between the two regions was not eliminated, but rather altered. Secondly, most of the photon energy was used by the normally pigmented skin to the detriment of achromic regions; these reflect light better, due to their clear colour, and are therefore much less susceptible than darker regions. Finally UVA rays penetrate down to the dermis and attack its fibres, thus triggering a degeneration process known as photoaging (skin aging caused by light). While such phenomena represent an inevitable outcome of this kind of phototherapy, they may also result from exposure to sunlight (Fig. 11).   In order to minimize irradiation, UVA rays were later combined with photosensitizing agents, which cause a hyper-reaction of the skin to luminous rays. The so-called PUVA-therapy was thus introduced (see OTHER TREATMENTS FOR VITILIGO, a term that refers to various treatment methods carried out by means of UVA lamps and photosensitizing psoralens. The PUVA-therapy shares some of its drawbacks with UVA rays, but these add up to secondary phenomena and contraindications to psoralens. General-diffusion UVB generators are also used for vitiligo treatment, also combined with photosensitizing agents, but this method involves the same problems as the PUVA-therapy, resulting from total body exposure (Fig. 12). Such problems may be solved for good by means of new UVB microirradiation techniques  (see THE NEW TREATMENT) (Fig. 13).