Which of the following is a potential side effect of laser hair removal?

Temporary redness and swelling in the treated area is indeed a recognized side effect of laser hair removal. This reaction occurs due to the heat generated by the laser, which targets the hair follicles while simultaneously affecting the surrounding skin. The redness and swelling are typically mild and resolve within a few hours to a few days following the procedure, indicating the skin's natural response to the treatment.

While other options suggest various outcomes, they do not accurately reflect typical side effects associated with laser hair removal. Permanent hair loss would not occur in untreated areas, and immediate skin tightening is not a guaranteed outcome following each session; instead, some patients may experience a slight temporary tightening effect, but it is not the primary purpose of the treatment. A lasting darkening of the skin is also not common and would typically resolve over time, making temporary redness and swelling the more accurate association with side effects post-laser hair removal.