Your armpits are not complicated—but if you don’t properly tend to them, you could face the sweaty, smelly consequences. I, for one, have ruined many, many t-shirts simply by virtue of my leaky armpits, as my sweat mixes with antiperspirant, causing stains. Sometimes, these stains are permanent, forcing me to retire my most beloved garments.
Which begs the question not only for me, but for all my sweaty kindred spirits out there: How much deodorant or antiperspirant is the right amount? The answer, unlike your armpits, is a bit more complicated than meets the eye.
The difference between deodorant and antiperspirant
First, a key distinction. Deodorant is different from antiperspirant, at least in theory (nowadays most deodorants are antiperspirants, so you’re usually getting a mixture of the two regardless). Antiperspirant is crammed with aluminum compounds that plug your sweat glands so you drip less. Deodorant is more of a fragrance that prevents your pits from smelling.
Adam Mamelak, a dermatologist with Sanova Dermatology explained in 2015 regarding antiperspirant that “the percentage of aluminum chloride essentially helps reduce the amount of sweat that is produced” by plugging up your sweat glands on a temporary basis. While antiperspirant is designed with the dual purpose of stopping sweat and preventing body odor, deodorant is purely for the latter. So, basically, less-sweaty people don’t need to use the aluminum-based products (which, by the way, can present health issues if used in excess, especially when a person has poor kidney function).
That may sound alarming and unexpected, and even if you may have heard that excessive antiperspirant use can lead to breast cancer, these rumors are largely unfounded, according to the American Cancer Society. The only health concern that stems from using excessive antiperspirant applies to the aforementioned people with poor kidney function. According to Benjamin Chan, a physician at Penn Family Medicine in Phoenixville, Pennsylvania, “aluminum might be of greater concern if you have kidney problems, especially if your kidney function is about 30 percent or less.”
He expanded on the issue in a 2019 article for the University of Pennsylvania medical center:
Too much aluminum in your body can cause bone diseases or dementia. Usually, excess aluminum is filtered out of your body by your kidneys. So, people with weakened kidney function can’t filter aluminum fast enough. However, if you have normal kidney function, your kidneys can usually process the amount of aluminum from antiperspirants and cosmetics that is absorbed through your skin.
That said, you’re probably fine using as much antiperspirant as you want, but using too much of it is a waste of antiperspirant, and your money.
Sweat is actually odorless
Even though antiperspirants are primarily meant to tackle sweat, it isn’t sweat alone that makes you smell.
“There are apocrine and eccrine glands in the armpits,” New York Demotologist Rebecca Kleinerman tells Lifehacker. “Apocrine glands under the arms produce thicker secretions, which bacteria on the skin break down and cause an unpleasant odor.”
As the Mayo Clinic explains further, body odor is the natural product of lingering bacteria breaking down into acids once it merges with sweat.
Apocrine glands are found in areas where you have hair, such as your armpits and groin. These glands release a milky fluid when you’re stressed. This fluid is odorless until it combines with bacteria on your skin.
If you’re sweatier than normal—like me, whose pits drip even when I’m just sitting here and working—you probably want an antiperspirant deodorant. Luckily, combinations of the two are readily available wherever you can buy deodorant.
How much is the ideal amount to apply?
There is no exact protocol for every armpit, nor is there a bounty of medical research that pinpoints the ideal amount of antiperspirant or deodorant to apply. Brands often extol the benefits of their own products when used according to their own purportedly trial-tested methods, but there’s nothing to suggest two swipes of antiperspirant is better than three or four.
Regardless of whether you suffer from excessive sweating (known as hyperhydrosis in medical parlance), Dr. Kleinerman advocates a measured approach to deodorant, telling Lifehacker:
Aluminum antiperspirants are meant to be applied as a thin film over the axillary vault; adding more so that it chunks and flakes off isn’t necessarily helpful as it’s not making contact with the ducts, although the deodorant may smell nice as you are adding fragrance.
In theory, a regular, over-the-counter antiperspirant is supposed to last between six and eight hours, according to Kleinerman. For the prescription strength stuff, she says, “you can repeat application every 24-48 hours until … control of sweating [improves], and then apply a couple times weekly to keep under control.”
Additionally, there’s one scientifically valid method for reducing sweat with antiperspirant that might seem a bit counterintuitive: applying it at night.
Why should I use it at night?
This sounds odd, but it’s common knowledge among dermatologists that applying antiperspirant at night before bed is more effective than putting it on before starting your day.
This is something Lifehacker broached in 2014, and despite this publication’s best efforts, it still might be a somewhat overlooked nighttime ritual.
As Lifehacker’s former staff writer Patrick Allan wrote at the time:
The night is the best time for application because your sweat glands are less active and your skin is drier. The effect of the ingredients usually lasts around 24 hours and will remain active when you shower in the morning because the pores will still remain plugged. So, if you haven’t already, switch up your daily routine and add antiperspirant to the night shift. If you’re not sure of what kind of deodorant to buy, take a look here.
This knowledge is echoed by Kleinerman, who says that aluminum antiperspirant products work by “blocking/interfering with your eccrine duct secretions, so applying them at night is recommended.”
What about alternative methods for stopping sweat?
If you’re at your wit’s end after exhausting all of the sweat-stopping measures at your disposal, you might be enticed by a botox injection in the armpit. This can be very effective, albeit temporarily.
Kleinerman tells Lifehacker:
Injectable botox works nicely for axillary hyperhidrosis by blocking nerves from releasing a neurotransmitter which stimulates eccrine glands to release sweat. This blockade lasts about 3 months and then wears off.
As for even more experimental methods, such as using rubbing alcohol to stymie the leakage, Kleinerman says it “may temporarily decrease the bacteria on the skin which contributes to bromhidrosis (body odor),” but it won’t work as a longterm solution for stopping sweat.
The takeaway, when it comes to your beleaguered pits, is to find the recipe that works for you. But if you aren’t one to use prescription grade antiperspirant, or undergo three or four rounds of botox per year, you might try applying antiperspirant at night, and just coping with the sweat if it persists.