Dear Christopher Cat: Amanda, my arthritic cat, enjoys napping in the sun’s warmth by the window. I just read that sunshine can give her cancer. Would a sheer curtain block enough sun to protect her? Christopher Responds: You are correct that ultraviolet light, particularly the UVA rays that pass through windows and penetrate deeply into the skin, can cause skin cancer, usually squamous cell carcinoma. The regions of the body most often affected are the nose, ears and other areas where hair is sparse or pink skin lies beneath white hair. A sheer curtain would cut down on some of the light, but the UVA rays that reach Amanda’s skin would still pose a risk. A better solution is to apply ultraviolet-blocking film to the window. It will stop the harmful UVA rays from reaching Amanda but still let the heat through to warm her.