All laser treatments have virtually the same set of side effects. The difference is in their rate of occurrence. Side effects occur due to the effects of the laser treatment like, heat, spreading beyond the targeted chromaphore to the nearby tissues. Current techniques like selective photothermolysis can accurately target the chromaphores. Nevertheless, errors do creep in due to reasons, such as, low operative skill, patient traits, skin pigmentation, pre-existing medical conditions, sun exposure or improper wound care. Generally, continuous wave lasers, which target less accurately, cause more side effects than pulsed lasers.

Side effects caused by various laser treatments

In vascular-specific laser treatment: The most common side effect is hyperpigmentation due to crusting caused by laser irradiation. Pulsed dye treatment causes purpura and hyperpigmentation. Hyperpigmentation cures spontaneously without medication though topical creams may quicken the recovery. Hypopigmentation is less common, caused by epidermal melanin absorbing the laser energy. Skin texture changes and scars are possible if excessive power density and overlapping laser spots are used.

In pigment specific laser treatment: The most common side effects observed in this treatment are changes in skin pigmentation. Continuous wave pulse produces more changes in both skin pigmentation and texture. In some pulsed lasers, hypopigmentation occurs, possibly due to increased melanin absorption at 694nm wave length. Usually low fluence leads to hyperpigmentation and excessive fluence leads to hypopigmentation.

In tattoo laser treatment: This laser is also used to target cutaneous melanin and hence hypopigmentation is the most common side effect in this treatment. Hypopigmentation usually resolves after sun exposure. If the tattoo pigment contains iron oxide, then immediate and permanent skin darkening occurs in pulsed lasers, due to reduction of ferric oxide to ferrous oxide. Vesiculation and crusting may occur due to high energy density or due to tattoos with dense ink deposition. Changes in skin texture can be prevented by using the correct fluence and by early treatment.

Side effects in laser-assisted hair removal

Perifollicular erythema and edema occur in all patients and resolve in a few hours. The intensity and duration depend on hair color, hair density, and fluence. The reaction usually lasts 1-3 days. Epidermal damage occurs if excessive fluence is used. It is also more common in patients with a tan.

Transient pigmentary changes, such as hypopigmentation and hyperpigmentation can be prevented if the correct fluence is chosen and if the patient is ideal. Hypo pigmentation may be permanent and occurs more in dark-skinned individuals. Scarring is unlikely except in cases of overaggressive treatment or postoperative infection. Lightening of tattoos and loss of freckles or pigmented lesions is not uncommon.

In cutaneous laser resurfacing: This laser is recognized for producing side effects with the highest rates of occurrence. The CO2 laser, even with proper procedures, correct parameters and antibiotic prophylaxis, produces changes in skin texture, skin color and infections.

Prolonged erythema, lasting months after treatment, is seen in all patients. Contact dermatitis is also a common side effect, due to probably an impaired skin barrier function. Thick emollients and occlusive dressings may cause milia and aggravate an existing acne condition.

A temporary hyperpigmentation is commonly seen a month or so after treatment. It slowly clears spontaneously but suitable topical applications can speed up the recovery. Unlike the temporary hyperpigmentation, hypopigmentation, with this laser, is a delayed and permanent occurrence. It appears within six months and may not be evident even one year after treatment. It is seen without any bias in all skin types, though it is more frequent in skin that has received dermabrasion or phenol peeling. Mild glycolic acid can reduce the impact. Unfortunately, exposure to the sun makes this type of hypopigmentation more prominent because they do not tan the normal way.

In laser-assisted blepharoplasty and endoscopic forehead lifting: Side effects which occur after laser treatment can also occur after any surgery done concurrently. With these types of surgeries the most feared side effect is bleeding inside the orbit leading to high intraocular pressure and perhaps loss of vision. Further surgeries are needed to resolve these conditions.

Surgeries cause scarring and any skin incision can cause an unacceptable level of scarring. Such scars can be made less prominent by further laser treatment or by other methods. More severe side effects like hypertrophic scarrings are rare. Though correct laser parameters can reduce the chances of such scarring, isotretinoin use, cosmetic procedures and tendency to form keloids can be risk factors.

Blepharoplasty sometimes results in a unique side effect which is the formation of a subjunctival bleb filled with straw colored fluid. The cause is not known but the condition does not worsen.