Why Do My Underarms Smell? Causes and How to Fix Body Odour

Underarm odour is not caused by sweat itself. Fresh sweat is almost odourless. The smell appears when skin bacteria — mainly Corynebacterium and Staphylococcus species — break down the protein-rich and fatty secretions of the apocrine glands in your armpits into volatile thioalcohols and short-chain fatty acids. Those breakdown products are what you actually smell.

Why do underarms smell in the first place?

Body odour is a three-part equation: a gland, a secretion, and a bacterium. Your body has two kinds of sweat gland, and only one of them produces the secretion that leads to smell.

Eccrine glands cover nearly your whole body and release a thin, salty, largely odourless fluid whose job is cooling. Apocrine glands are concentrated in the underarms, groin and around the nipples, they only switch on at puberty, and they release a thicker secretion containing proteins, lipids and steroids. That secretion is also odourless when it leaves the gland. It becomes smelly only after resident skin bacteria digest it.

This is why the same person can run for an hour and have odourless sweat on their back, but a distinct smell under their arms. It is also why odour is a skin surface problem, not a hygiene failure — and why it responds to what you put on the skin.

What makes underarm odour worse?

Odour intensity depends on how much apocrine secretion is available and how well bacteria thrive on your underarm skin. Several everyday factors push both up, and most of them are especially relevant in Indian conditions.

• Heat and humidity. Warm, damp skin is an ideal growth environment for Corynebacterium. Summer and monsoon months genuinely do smell worse.
• Trapped moisture. Synthetic fabrics and tight sleeves hold sweat against the skin instead of letting it evaporate. Cotton and looser cuts help.
• Underarm hair. Hair increases surface area and holds secretion close to the skin for longer, giving bacteria more contact time.
• Diet. Sulphur-containing foods such as garlic, onion and cruciferous vegetables, plus alcohol and some spices, can alter the smell of sweat for several hours.
• Stress. Emotional stress preferentially triggers apocrine glands — which is exactly the sweat that turns smelly. This is why "nervous sweat" smells stronger than exercise sweat.
• Shaving irritation and razor bumps. Broken, inflamed skin disrupts the barrier and shifts the surface microbiome. If this is your pattern, read our guide to razor bumps after shaving.
• Not drying properly. Pulling clothes onto damp underarms after a shower gives bacteria a head start before you have even left the house.

Deodorant or antiperspirant — which do you actually need?

These are two different products solving two different problems, and most people who complain that "deodorant doesn't work for me" are using the wrong one.

If your issue is smell rather than visible wet patches, a well-formulated deodorising treatment is the correct choice — and it can do more than mask. Actives that gently lower surface pH and reduce dead-cell buildup make the underarm a less hospitable surface for the bacteria doing the damage.

How to reduce underarm odour, step by step

The goal is not to stop sweating — sweating is how you regulate temperature. The goal is to change the surface conditions that let bacteria convert sweat into smell.

1. Wash the underarm properly, twice daily in hot weather. A gentle cleanser and 20 seconds of actual contact beats a quick rinse. Our simple body care routine covers the order.
2. Dry completely before dressing. This single habit makes a measurable difference and costs nothing.
3. Use a treatment product with real actives, not just fragrance. 5% AHA gently exfoliates and helps keep the surface pH low, which suits the skin better than the near-neutral pH odour-causing bacteria prefer. 4% Niacinamide supports the barrier so the area tolerates that exfoliation.
4. Apply to clean, dry skin — not over old product, and not immediately after shaving, when skin is most reactive.
5. Rethink fabric before you rethink hygiene. Breathable cotton and a change of shirt on a 40°C day often outperform a stronger product.
6. Give it two to four weeks. Surface conditions shift gradually. Judging any underarm product on day two is judging it too early.

Does odour control help with dark underarms too?

Often, yes — because the two problems share causes. Friction, shaving irritation and product-related irritation drive both post-inflammatory pigmentation and barrier disruption. Reducing that irritation while gently exfoliating helps on both fronts, which is why treatment roll-ons commonly combine exfoliating and brightening actives. If darkness is your main concern rather than smell, our detailed guide to brightening dark underarms and evening body tone goes deeper.

When should you see a doctor?

Most underarm odour is normal physiology and responds to surface care. See a dermatologist if you notice a sudden change in your usual body odour with no change in diet or routine; sweating heavy enough to soak clothing at rest, which may be hyperhidrosis; a persistent odour that no topical product improves, sometimes called bromhidrosis; or red, scaly, itchy underarm skin, which may be a fungal infection or contact dermatitis rather than an odour problem at all.

FAQ

Does sweat itself smell?

No. Both eccrine and apocrine secretions are essentially odourless when released. Smell is produced when skin bacteria metabolise apocrine secretion into thioalcohols and short-chain fatty acids.

Why do my underarms smell even after a shower?

Usually because bacteria remaining in the hair and follicles begin working on fresh secretion within a couple of hours, or because you dressed before the skin was fully dry. A treatment product applied to clean, dry skin extends the fresh window considerably.

Does shaving reduce underarm odour?

It can help by reducing the surface area that holds secretion, but shaving irritation can worsen the skin barrier and pigmentation. If you shave, do it in the evening and apply treatment products the next morning rather than immediately after.

Can food cause body odour?

Yes, temporarily. Sulphur compounds from garlic, onion and cruciferous vegetables, as well as alcohol, are partly excreted through sweat and can alter its smell for several hours to a day.

How long does an underarm roll-on take to work?

For odour, most people notice a difference within the first week. For tone and texture, give it four to eight weeks of consistent daily use — pigmentation changes slowly, and no topical works overnight.

Is it safe to use an AHA product on underarm skin?

Underarm skin is thin and folds on itself, so it needs a formulation designed for that area rather than a face exfoliant. A 5% AHA buffered with 4% Niacinamide is formulated for this. Apply to intact skin, avoid application straight after shaving or waxing, and stop if you get persistent stinging.