Deodorants and antiperspirants are both modern inventions that didn’t exist before the 1800s. Before then, people typically used perfumes and colognes to mask their odor. The first deodorant on the market was called Mums, which launched in 1888, while the first antiperspirant, Everdry, launched in 1903. The body odor product category wasn’t mainstream for several decades after either launch, though. It was only after a targeted campaign in Ladies Home Journal for the product Odo-ro-no that framed body odor as a reason for shame that the categories exploded. Now, deodorants and antiperspirants have become as normalized as the shame that made them popular. Here’s how to tell them apart:

Deodorants are classified as cosmetics by the FDA and mask odor with a kind of fragrance and minimize the odor caused by bacterial breakdown of sweat. It’s actually the fragrance composition in most deodorants that is suspected of causing dermatitis (skin irritation) in a lot of consumers, according to this heavily cited study.

Antiperspirants are classified as over-the-counter (OTC) drugs because they prevent sweat point-blank, acting as a temporary plug for the sweat ducts. To do so, they commonly use aluminum salts, which dissolve in the sweat and form a gel. The aluminum in antiperspirants generally makes up 10-25% of the active ingredients.

Here’s a bullet point list to remember:

• Deodorant blocks odor.
• Antiperspirant blocks sweat. It does not block odor.
• Using both means you’d block both odor and sweat.
• There’s no substantial scientific evidence that links either to cancer. The FDA has a pretty clear-cut explainer on the subject.
• Sweat itself is odorless. It is the breakdown of bacteria that causes the smell.
• Either way, you can still get sweat stains — but these can be resolved with spot-treating with vinegar.