Shop Chewy Pharmacy for the best pet prescription medications online! We carry a wide variety of prescription flea & tick, diabetic, heartworm, skin & coat, arthritis and more. *FREE* shipping on orders $49+ and the BEST customer service! Find patient medical information for Selsun Blue topical on WebMD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. Wet the skin before applying, gently work up a lather for 10 to 20 seconds, and rinse thoroughly. Do not scrub the skin. If using the shaving cream, first wet the area to be shaved. Apply a small.