Maybe you noticed after exercising at the gym [1], or perhaps one day while sitting at your desk in the office [2], but your deodorant doesn't seem to be working anymore. Is that possible, or are you imagining it? It's true, this frustrating issue can happen and we asked an expert why.

"It's not uncommon for people to feel as though their deodorant is no longer as effective as it once was," says Erum Ilyas, MD, a dermatologist at Montgomery Dermatology [3] in King of Prussia, PA. "The most important step to figuring out why is understanding the difference between antiperspirant and deodorant [4]. Antiperspirants block sweating; deodorants mask odor [5], which comes from the combination of sweat plus bacteria." Knowing that, there are two possible scenarios for what you're feeling: either there is more sweat than there was before, or there are more or different kinds of bacteria present that create odor. No matter what category you fall in, there are ways to fix the problem.

"If there is a damp feeling along with odor, we have to re-evaluate our game plan with sweat by increasing the strength of the antiperspirant," says Ilyas. If you find that excessive sweating is the root of your problem, you might want to look at clinical-strength antiperspirants, such as Secret Clinical Strength Sport [6] ($12), which can offer up to four times more the amount of protection than ordinary antiperspirants.

Not excessively sweating, but finding yourself in a stinky situation? "If there is a dry feeling but odor, then it may help to change up your deodorant scent choice for something stronger, add an antibacterial soap or lotion for a week or two to cut down on bacterial overgrowth, or consider using a mild scrub in the area to gently exfoliate any buildup of bacteria," says Ilyas.