Hyperpigmentation (Fig. 11.1) is a very common complication and possibly the most common in darker skin types (see the study by Sriprachya-anunt and colleagues). It has been described with the use of almost every laser and light device in darker skin types. In one study by Moreno-Arias and co-workers, it was observed in 16% of patients undergoing IPL treatment. Goh reported that it can be as high as 45% in patients with skin types IV–VI. Wareham et al reported that the pulse dye laser can cause hyperpigmentation, especially on the lower legs and where there is inadequate post-treatment sun protection and sun avoidance. Hyperpigmentation was also seen by Chowdhury and colleagues with the KTP laser. With the ablative CO₂ laser, post-inflammatory hyperpigmentation (PIH) is common and was reported by Badawi et al to occur in 20–30% of Fitzpatrick III and 100% of Fitzpatrick IV patients. Mahmoud et al found the Er : YAG laser to have a PIH rate of 50% in patients with skin type IV–V (Fig. 11.2). Even non-ablative fractional lasers can cause problems with PIH; in a 2010 study by Chan et al there was an 18.2% rate in 47 patients treated. Although rarer, PIH has also been reported (e.g. by Choudhary et al and Kuperman-Beade et al) to occur with the use of Q-switched lasers. In darker skin types, it can be fairly common; it was reported by Lapidoth & Aharonowitz to occur in up to 44% of darker-skinned patients. As noted above, vascular lasers were also found by Clark et al to result in PIH, albeit more rarely.

Figure 11.1 Post-inflammatory hyperpigmentation following treatment with the Q-switched Nd : YAG laser.

Figure 11.2 Post-inflammatory hyperpigmentation following treatment with the erbium : YAG laser.

Hypopigmentation is a less common complication and is most commonly seen with the use of Q-switched lasers for tattoo removal as well as vascular lasers for port-wine stains. Hypopigmentation from Q-switched lasers may be transient, but it can also be permanent. Depigmentation was also reported (by Fitzpatrick & Goldman) to occur with Q-switched lasers. In the treatment of port-wine stains, the pulse dye laser has incidence rates of 2–31% of hypopigmentation. Longer pulse durations with the pulse dye laser seem to lessen the possibility of this complication. The ablative lasers have all been found to cause hypopigmentation (e.g. studies by Trelles and by Ward & Baker). Permanent hypopigmentation has also been described with the use of the CO₂ laser and, in a recent 10-year follow-up study by Prado and colleagues, 8.7% of patients had problems with permanent hypopigmentation.

Reactivation of herpes simplex virus (HSV) is a possible complication for which prophylactic antivirals are often given, especially with resurfacing lasers. However, in a recent retrospective study by Trelles of patients not given antiviral prophylaxis, less than 1% of 600 patients developed reactivation of HSV with the use of a resurfacing laser. In another retrospective study by Campbell & Goldman, only 1.1% of 373 patients developed herpes reactivation with fractionated CO₂ laser resurfacing. Despite a low incidence rate, the potential for scarring with disseminated HSV infection can make this a serious complication.

Acneiform eruptions can occur with any laser and light device and may be due to either procedure or after care. Reported rates depend on the treatment, but in the three studies by Campbell & Goldman, Nanni & Alster, and Neaman et al they ranged from 3 to 15% of patients with resurfacing lasers. This is a relatively benign complication with self-resolution expected.

Scarring has been reported with almost every cutaneous laser and light source (Figs 11.3–11.6). The actual incidence is fairly small, yet overaggressive treatment with any laser or light device can cause it. Hypertrophic scarring is most common with the older continuous wave lasers, most of which are no longer commonly used in office practice.

Figure 11.3 Hypopigmentation and scarring following treatment with the pulsed dye laser.

Figure 11.4 Scarring following treatment with the carbon dioxide laser.

Figure 11.5 Scarring following laser hair removal.

Figure 11.6 Scarring following treatment with an intense pulsed light.

Specific laser complications

The complications covered above are common to almost all laser and light devices. However, there are some specific complications or considerations of various subsets of lasers.

Q-switched lasers

In the study by Kuperman-Beade and co-workers, the most common adverse effects of the Q-switched lasers included hypo- and hyperpigmentation, textural change, and scarring after treatment (see Fig. 11.1). Melanin is the main competing chromophore and transient hypopigmentation as well as permanent depigmentation with the Q-switched ruby laser can be seen (see the study above and those by Bernstein and Choudhary et al). Grevelink et al found that the Q-switched Nd : YAG laser with its longer wavelength has less chance of hypopigmentation than the Q-switched ruby laser. In darker-skinned individuals, if a Q-switched laser other than the Nd : YAG laser is used then decreasing the fluence may help prevent hypopigmentation, according to Kuperman-Beade et al.

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