Did you know you can shed 4 litres of sweat an hour?

Sweat has important functions, including cooling you down when it’s hot outside. Here’s what science says about using antiperspirants and deodorants, says Keren Landman

Keren Landman: Sweating to cool down is a genuine superpower, keeping the body functional in heat that would incapacitate most other animals. Picture: iStock

Every day, 5bn people around the world reach for deodorant. Many of us assume that managing, modifying, and hiding sweat is an absolute necessity — and not just in your armpits.

Routine underarm antiperspirant and deodorant use are unlikely to cause harm. But do you know what sweat is actually for, and what these products actually do?

What’s the purpose of sweat?

Sweating to cool down is a genuine superpower: A well-trained human can shed nearly four litres an hour, keeping the body functional in heat that would incapacitate most other animals.

Sweat also has a social dimension. The odour that rises from your body — not the sharp armpit kind, but the ambient chemistry that makes you recognisable to your loved ones — results from compounds circulating in your blood, the output of your oil glands, and the unique microbial ecosystem living on your skin.

Siblings can identify each other by smell and the scent of someone you love can surface a memory faster than any other sense.

Are antiperspirants and deodorants the same thing?

No, and the difference matters more than most people realise.

Antiperspirants physically block your sweat ducts using aluminum-based compounds, which form a temporary gel plug that prevents sweat from getting through.

This plug continues to move out of the duct over time, which is why you need to reapply it periodically.

Deodorants target sweat once it’s already on your skin, using fragrances and acids that make the skin’s surface less hospitable to odour-causing bacteria, or compounds that chemically neutralise smelly molecules.

In the European Union, they’re regulated as cosmetics, not drugs. As antiperspirants actively change the body’s natural functions, they often straddle the line between a cosmetic and a medicinal/biocidal product.

The claim that antiperspirant aluminum causes breast cancer or Alzheimer’s has been extensively studied and consistently disproved.

Does blocking sweat in your armpits interfere with cooling?

Not in any meaningful way. Eccrine glands, which are responsible for cooling you down, cover almost your whole body. The apocrine glands in your armpits and groin produce a thicker, waxier fluid that certain bacteria love to eat; those bacteria produce what we call body odour as they digest it.

Blocking a few sweat glands in an area not primarily responsible for temperature regulation won’t compromise your ability to stay cool.

Should I use a whole-body deodorant?

If you’re considering whole-body products, it’s worth pausing to ask what problem you’re actually trying to solve.

The eccrine sweat covering the rest of your body is largely inoffensive; it doesn’t give bacteria much to work with. If you’re cleaning your body regularly, there is probably no genuine hygiene problem to solve on, say, your shins or your forearms.

Certain foods and medications can temporarily affect the odour of your eccrine sweat, and certain medical conditions can cause a strong unpleasant odour in a range of body sites. But for most people, the ambient smell of your body isn’t the armpit kind.

When it comes to performance, whole-body deodorant sprays aren’t much more than alcohol and fragrance: Essentially, diluted perfume. Creams and sticks are more substantive and contain acids or odor-neutralising compounds.

But eccrine sweat doesn’t typically contribute to odour, so they’re mostly useful in apocrine-rich areas like the armpits and groin.

For these areas, it’s probably fine to use a product on intact, non-irritated skin. (Avoid use on just-shaved areas.) Just don’t expect it to reduce how much you’re sweating.

“Suggesting you should put some of this all over your body is not biologically based,” says Adam Friedman, a dermatologist at the George Washington University in the US.

What if I sweat excessively?

Hyperhidrosis, in which the body produces far more sweat than it needs for temperature regulation,
affects about 5% of people. For those who live with it, it’s genuinely disabling: This volume of sweat can soak through clothing or make it difficult to grip things, and can cause significant anxiety.

Over-the-counter deodorants are inadequate for treating these symptoms, says Friedman, who is also a faculty member of the International Hyperhidrosis Society. He often recommends prescription topical medications and Botox injections as therapy, sometimes off-label.

If you think you might be affected by hyperhidrosis, a dermatologist with experience in the condition is the right starting point.

Is my usual deodorant routine OK?

If your current approach is working and you’re not bothered by
symptoms, there’s no reason to change it. Routine antiperspirant and deodorant use in the underarms is safe and effective for most people.

If you have symptoms you want to address, see a clinician rather than reaching for an unproven cosmetic product.

For most people, a daily shower and a standard underarm deodorant or antiperspirant covers it.

The Guardian