Blue LED light is most often used to treat acne. It may do this by reducing activity in the sebaceous glands, so they produce less of the oil that can plug the hair follicles, leading to acne.

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Blue light may also kill acne-causing bacteria known as Cutibacterium acnes.

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Often blue and red light are used in combination to help fight acne — the blue light targeting the C. acnes and the red light targeting inflammation and redness.