"Blue light therapy is most commonly used to treat sun damage and premalignant or malignant skin cancer growths. It can actually be used to prevent skin cancer and remove both precancerous skin lesions and cancerous skin lesions that haven’t spread to other areas of the body (or metastasized).
Photodynamic therapy can be used to treat skin cancer. It causes the photosynthesizing drug that’s been applied to the skin to react with oxygen, killing the cancer cells. It may also be used to trigger an immune system defense or damage the blood vessels feeding the cancer cells."
"Immediately following treatment, the area may be red, swollen, tender, and mildly bruised or blistered, especially when medication has been applied to the skin. The treated area may crust over or peel, but this is considered normal. Most people heal within 7 days, and the crusting resolves within 3 to 14 days."
www.healthline.com
I had never heard of this, but as he wrote in his post "Blue Light Therapy
skin cancer prevention day 3", it sounds like BG is doing this as a preventative measure after all those years playing in the sun.
On a related note, I seem to recall that the reason Gilbert wore sunglasses in the later part of his career and when coaching is because he had sun damage to his eyes. Seems logical that his skin would have taken some damage as well.