Fish-eye, warts and calluses are diseases where the skin thickens. There are several ways to remove the eyes of fish, warts, and calluses. One way is to use topical medication containing keratolytic substances (skin thinning), such as salicylic acid. Fish-eye, warts and calluses usually occur in the feet and hands, but can also appear in any part of the body. Calluses generally do not cause pain, whereas fish eyes and warts can be painful if they are stressed or subjected to friction. Causes and Symptoms of Fish Eye, Warts and Calluses Both fish and calluses appear as a form of skin protection against friction or pressure. Repeated friction or pressure causes thickening of the skin. Wearing shoes that don't quite fit, often not wearing socks, playing musical instruments like a guitar, or often using hand tools, can increase the risk of forming fish or calluses. Both of these conditions are not contagious. Meanwhile, warts are caused by viruses from the human papillomavirus (