The invention is based, at least in part, on the discovery that if a tissue is irradiated with a sublethal dose of radiation, e.g., from a laser, that pigmented cells in the tissue are selectively stimulated to proliferate and to produce higher levels of certain mitogenic factors and growth factors such as platelet derived growth factor (PDGF). In particular, the various parameters of a pulsed laser beam, such as power, pulse duration, total radiation energy ("fluence"), wavelength, and if multiple pulses are used, the pulse rate and total number of pulses, are carefully selected and controlled to minimize killing the irradiated pigmented cells.
