Before you go to sleep, apply your antiperspirant. “A good way to boost the efficacy of your antiperspirant is by putting it on bone-dry skin,” says Saryna Young, MD, a dermatologist with the Westchester Medical Group in White Plains. “That’s why we recommend doing it at night. If you apply it in the morning after you shower, you usually still have some moisture on your skin, which will dilute and dissolve the product and wash it away before it can reach and block the sweat ducts.”
You can still shower in the morning—with no need to reapply. “If you leave it on for six to eight hours while you sleep, it will block the sweat ducts”—for up to 24 hours.