Studies show some of the chemicals in coal tar may cause cancer, but only in very high concentrations, such as in what is used in industrial paving. Anyone using tar regularly should follow a regular skin cancer checkup schedule. California requires OTC coal tar shampoos, lotions and creams that contain more than percent coal tar to be labeled with cancer warnings. However, the FDA maintains that OTC products with coal tar concentrations between percent and 5 percent are safe and effective for psoriasis, and there is no scientific evidence that the tar in OTC products is carcinogenic.
Dog food itself can have a positive impact on dogs that are suffering from arthritis. In a clinical study, dogs that were fed a diet specifically formulated for dogs with OA (osteoarthritis) such as Hill's Prescription Diet j/d , a food rich in Omega-3 fatty acids , showed improvement over dogs that had a similar arthritic condition, but that were fed an ordinary diet. The results of the study showed that "more dogs in the test group had a reduction in pain at the end of the 90-day trial." 82% of the dogs in the trial that received the new diet showed improvement.