Fish gelatin is commonly used in blocking solutions to minimize background noise in immunodetection procedures such as Western blotting and immunostaining. Because this gelatin is derived from the skin of cold water fish it does not cross-react with mammalian antibodies. Fish gelatin can be used in blocking buffers to block non-specific binding sites on positively charged nylon or PVDF membranes or for blocking and dilution of antibodies during immunostaining procedures.