PSI Barbering Practice Exam 2025 – All-in-One Resource to Master Your Certification!

The correct choice for the color of light that is effective in reducing acne and bacteria is blue light. Blue light has been shown to have antimicrobial properties, specifically targeting the bacteria known as Propionibacterium acnes, which is one of the primary contributors to acne development. When skin is exposed to blue light, it penetrates the skin and directly affects these bacteria, reducing their population and subsequently decreasing the occurrence of acne.

In contrast, while red light is beneficial for reducing inflammation and promoting healing, it does not have the same targeted antibacterial effects as blue light. Ultraviolet light, often used in certain medical treatments, can actually exacerbate skin issues, including acne, and may lead to skin damage. Green light is primarily used for pigmentation issues and does not specifically target acne-causing bacteria. Thus, blue light stands out as the most effective for treating acne due to its direct action against harmful bacteria.