The effect of phototherapy on Demodex density: a case-control study

Area of Science:

• Dermatology
• Microbiology
• Immunology

Background:

• Human Demodex mites (Demodex folliculorum and Demodex brevis) inhabit pilosebaceous units asymptomatically.
• Previous research suggested a link between phototherapy and demodicosis.
• The current study investigates the impact of phototherapy on Demodex density and demodicosis prevalence.

Purpose of the Study:

• To determine if 20 phototherapy sessions increase Demodex density.
• To assess if phototherapy influences the frequency of demodicosis.
• To evaluate the relationship between phototherapy and Demodex mite infestation.

Main Methods:

• A case-control study involved 32 participants receiving narrowband ultraviolet B or ultraviolet A-1 therapy.
• Standardized skin surface biopsies were used to measure Demodex density before and after 20 phototherapy sessions.
• Demodex-related skin conditions were assessed, and statistical analysis compared pre- and post-treatment Demodex densities and demodicosis prevalence.

Main Results:

• No statistically significant change in Demodex density was observed after 20 phototherapy sessions (2.75 ± 4.48/cm² pre-treatment vs. 2.85 ± 4.81/cm² post-treatment; P=0.879).
• The prevalence of demodicosis showed no significant difference between baseline (28.1%) and post-treatment (31.3%) (P=1.00).
• These findings contradict previous suggestions of increased Demodex density and demodicosis following phototherapy.

Conclusions:

• The study's results do not support a link between phototherapy and increased Demodex density or demodicosis.
• Previous study conclusions regarding phototherapy-induced immunosuppression and Demodex infestation are debated due to methodological limitations.
• Larger, longitudinal studies with homogeneous samples are recommended to clarify the phototherapy-demodicosis relationship.