A. The most effective anti-perspirant is aluminum chloride (or deodorant). It is the only FDA approved product for underarm use. Some people, however, don’t like it because of its strong smell and white residue that can stain clothing. There are also products that claim to stop perspiration by blocking sweat glands or absorbing moisture through an oily surface layer on the skin. They often contain fragrances and colors but none have been proven safe for long-term use in humans over about one year of daily application. Those with sensitive underarms should avoid these products as well since they may cause irritation or allergic response similar to contact dermatitis from other substances used in cosmetics.