It sounds like witchcraft’: can light therapy really give you better skin, cleaner teeth, stronger joints?

Light therapy is certainly having a moment. You can now buy glowing gadgets for everything from skin conditions and wrinkles to sore muscles and gum disease, the latest being a toothbrush enhanced with tiny red LEDs, described by its makers as “a breakthrough in at-home oral care”. Globally, the market was worth $1bn in 2024 and is projected to grow to $1.8bn by 2035. You can even go and sit in an infrared sauna, where instead of hot coals (real or electric) heating the air, your body is warmed directly by infrared light. According to its devotees, it’s like bathing in one of those LED-lit beauty masks, boosting skin collagen, relaxing muscles, relieving inflammation and chronic health conditions while protecting against dementia.