Transient posttreatment hyperpigmentation occurs in i4%-25% of patients (Grossman et al. 1996; Bjerring et al. 1998; Williams et al. 1998), and is normally related to melanocytic-induced stimulation. The causes of this hyperpigmenta-tion include delayed tanning, epidermal injury, or an immediate pigment darkening phenomenon resulting from photo-oxidation of pre-existing melanin. The darkening is usually transient, lasting only 3-4 weeks and resolves without sequelae in most individuals (McDaniel
A potentially more serious hyperpigmenta-tion resulting from epidermolysis and blistering can occur at energy thresholds higher than those associated with immediate pigment darkening. This can be associated with permanent dyschromia.
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