Yes, permethrin 5% lotion is safe and correct to apply to the penis and scrotum. It is commonly prescribed to treat conditions like scabies or pubic lice, which cause intense itching. Typically, you should apply it to clean, dry skin from the neck down, covering all areas including the genitals, while avoiding the opening of the urethra. Leave it on for 8 to 14 hours (usually overnight) before washing it off. Some mild, temporary stinging or increased itching can occur. Because you were prescribed two other creams, please call your dermatologist's office to confirm the exact schedule and order of application for your complete treatment.