Deodorants and antiperspirants: What's the best kind of sweat-stopper?
Most deodorants and antiperspirants claim to last 24 or even 48 hours, but some people still end up re-applying multiple times each day.
The difference between a deodorant and an antiperspirant is simple. The former simply masks the smell of sweat, which is caused by bacteria and wetness; sweat itself doesn't actually have an odour. The latter blocks sweat glands altogether.
In reality, most items available in the personal care aisle are "antiperspirant deodorants", meaning they're a hybrid product that does both. But many people claim some brands work, and brands don't. Can any science tell us why?
The active ingredient in an antiperspirant product is usually aluminium chloride, aluminium chlorohydrate, or aluminium zirconium trichlorohydrate. So-called "clinical" antiperspirants often contain aluminium chloride hexahydrate or anhydrous aluminium chloride. All of these are aluminium ions that temporarily plug the sweat ducts in your armpits, disallowing sweat to flow through them onto the skin (and then your clothing).
Unfortunately, there's no good evidence to tell us which active ingredient is the most effective, or which percentage of that ingredient is required to actually block those ducts properly. The science behind antiperspirants and deodorants is vague and often only those with a condition called auxiliary hyperhidrosis (excessive sweating) are used in testing, not regular folk like you and me.
However, here's what the science can tell us: these products do work. Quantifying their effectiveness seems to be difficult, but studies – such as one this year from North Carolina Museum of Natural Sciences – confirm that they significantly reduce the level of the bacteria staphylococcaceae (one of our most common microbes) on the skin.
Also, we know that antiperspirants need time to work. Because people don't tend to sweat much at night, when applied during the evening a product can successfully plug those glands over a period of several hours, rather than being pushed back out through new sweat when applied in the morning.
Unfortunately, no product is going to work well for all people, because the degree to which a person sweats is genetic. Clinical-strength antiperspirants usually contain an aluminium concentration of 10 to 15 percent, and often come with statements from manufacturers that they're several times more effective than regular products. It's hard to find an antiperspirant manufacturer that has had a claim like this substantiated with rigorous independent studies, however, so we're largely left to take their word for it.
We do know that higher aluminium contents mean increased effectiveness against sweat.
The challenge here is finding a balance between function and comfort, as aluminium is highly irritative to the skin. Though there are studies proving the efficiency of prescription antiperspirants (which contain even higher aluminium concentrations than clinical-strength), but researchers note a key limitation in studying their use is compliance. That is, because high-aluminium antiperspirants are so uncomfortable (or even painful) to use, people just stop using them.
When a deodorant or antiperspirant manufacturer markets a product as "dermatologically tested", all that means is it has been tested on human skin. Rarely will the public be told how the tests were designed, what the sample size was, whether it was independently verified, or even if the product actually passed the test.
There's even been one study suggesting that the placebo effect of a high-strength antiperspirant is real. Published in the British Journal of Dermatology, it found that placebo testing resulted in 85 percent of study participants reporting reduced sweat – by half their usual volume – when told they were using a "clinical strength" product. As production of sweat in the apocrine grands (those in your hair follicles) is responsive to stress, this study result indicates how much emotions come into play in sweating, and how you may literally be able to trick yourself into sweating less.
There is no scientific proof to say whether an aerosol, roll-on, or stick-form antiperspirant or deodorant is more effective. It's a matter of personal choice. Aerosols are the driest in their application. Roll-ons are the most convenient to travel with. Sticks create a gel-like cover and potentially block the largest amount of skin.
Unfortunately, beyond that deodorant or antiperspirant use is trial-and- error, based on whichever brand and form you feel is most effective and comfortable for you.