Laser hair removal provides the permanent elimination of some but not all hairs. About 20 percent of all hair is in the resting phase (a phase in which the hair is less responsive to laser hair treatments), therefore complete removal is impossible. At best, 80 percent of the targeted hair may be permanently eliminated in some patients after several treatments. Treated hair that does regrow tends to be finer and lighter and the growth is delayed, with a longer delay than most conventional methods of hair removal (e.g., shaving, waxing, depilatory creams). Laser hair removal is less painful and faster than electrolysis.

Erythema (redness), edema (swelling) and pain may last several days to weeks after treatment. Other side effects depend largely on the type of laser and fluence (density of light) used and are rare if the procedure is performed properly by an experienced laser technician. Patients with tans or darkly pigmented skin are more likely to experience adverse effects because the melanin in the skin competes with melanin in the hair follicle to absorb laser light energy.

The most common side effects of laser hair removal are temporary pigment changes. Postinflammatory hyperpigmentation (darkening of the skin following inflammation) and hypopigmentation (lightening of the skin) have been reported. In some cases, bleaching creams or topical tretinoin (a retinoid) may be used to treat hyperpigmentation. A lightening or darkening of tattoos or freckles may also occur.

Other possible adverse reactions include burning, blistering, crusting and scarring. Outbreaks or flares of certain recurrent conditions may also occur, including psoriasis, vitiligo and herpes simplex virus. Some patients may also develop bacterial infections following treatment.