As with any prescription, you should, first and foremost, follow your healthcare provider's instructions. Instructions may vary depending upon the product prescribed and your individual situation. Generally, though, it’s recommended that prescription antiperspirants containing aluminum chloride remain on the skin for 6 to 8 hours and be applied before bedtime, when sweating is at its most minimal. Be sure your skin is dry and completely sweat-free before you apply the product - use a cool blow drier if necessary. Washing your skin before application is not necessary and may actually lead to greater irritation. If you shave your underarms, wait 24 to 48 hours after shaving before applying the prescription antiperspirant. If your skin gets irritated, treat it with a topical hydrocortisone cream and be sure to discuss it with your doctor. If your skin does not get irritated, use the antiperspirant every night until sweating is reduced. Once you’ve noticed that the antiperspirant has taken effect you may cut back on how often you use it.

You may have heard of people trying an "occlusion" technique to make their antiperspirants more effective. Occlusion is when you wrap the body area to which you've applied an antiperspirant in Saran or plastic wrap for an extended period of time, such as overnight. Please be advised that there is no evidence that occlusion improves antiperspirants' benefit. On the contrary, occlusion often causes severe skin irritation. If you are considering occlusion, talk to your doctor first.
 
If you can’t get relief using antiperspirants, or if skin irritation is severe, talk to a dermatologist about other excessive sweating treatments options including iontophoresis for hands and feet and Botox injections for hands, feet, underarms, face/scalp, and other body areas, or miraDry for sweaty underarms only.