Post herpetic neuralgia (PHN) is a painful condition and common complication of herpes zoster that affects the nerve fibers and skin. It is characterized by ongoing pain with varying degrees of skin hypersensitivity. The pain has been described as sharp, burning, stabbing that disturbs sleep, work, and other daily activities. The duration of PHN lasts more than 30 days. In some cases, the pain persists more long-term. Currently, no treatment available that diminish the incidence of PHN.

Low-level laser therapy (LLLT) is a noninvasive, pain-free, light-based therapy that uses red and infrared light to resolve the inflammatory process and eliminate pain. A retrospective review has been conducted of herpes zoster cases to evaluate LLLT reduce PHN incidence at acute and subacute stages of infection.

The study included 250 patients in acute, subacute, and control groups, respectively. It was found that the incidence of PHN was significantly lower in the acute group versus the control group after 1 month (odds ratio [OR] 0.21, P=.006, 95% confidence interval [CI] 0.068-0.632), 3 months (OR 0.112, P=.038, 95% CI 0.014-0.886), and 6 months (OR 0.123, P=.021, 95% CI 0-0.606). The subacute group only had a lower incidence (OR 0.187, P=.032, 95% CI 0.041–0.865) after 3 months as compared to control group.

Thus, LLLT helps to deactivate the herpes simplex virus, in turn reducing the incidence of post herpetic neuralgia. Further research is required to shed more light on this with the aid of well-designed randomized controlled trials.