Why does underarm sweat stink?

Why are armpits especially smelly?

Your armpits contain apocrine glands, sweat glands that release their secretions into hair follicles, the small openings where hair grows. These glands become active at puberty, which explains why underarm odor usually starts in adolescence. Apocrine secretions contain fats. When bacteria break those secretions down, they produce volatile acids, substances that evaporate and create the smell.12

Eccrine glands, the other main type of sweat gland, produce watery sweat that cools your body as it evaporates. Sweating more does not automatically mean smelling more: odor also depends on which bacteria live on your skin and how they interact with sweat. Heat, exercise and anxiety normally increase sweating, but dampness and odor are separate problems.23

Why does the smell change?

Hormones, foods, medications and skin infections can change body odor. Stress can activate apocrine glands, while hormonal changes during menopause can increase sweating. Garlic, onions and alcohol are possible odor triggers. Look for a repeated connection rather than cutting out foods at random. If a prescription seems linked to new sweating, discuss it with the prescriber; do not stop taking it without their advice.24

How to reduce underarm odor

1. 1Wash your armpits with soap at least twice a day and dry thoroughly. If soap irritates your skin, ask a pharmacist about gentler soap substitutes.
2. 2Remove sweaty clothing promptly, and change and wash clothes regularly. Choose loose clothing made from natural fabrics such as cotton rather than tight clothing that traps heat.
3. 3Choose deodorant for odor control, antiperspirant for sweat reduction, or a product combining both functions.
4. 4Apply antiperspirant to dry underarms before bed. If you have just showered or bathed, dry the skin before applying it.

Odor can cling to clothing, so yesterday's shirt can keep yesterday's contribution to the problem. Shaving underarm hair is another option that can help control odor, but the evidence for its effectiveness is limited. Hair removal is an option, not a required part of the routine.16

Does deodorant stop the sweat?

A deodorant can mask odor without reducing sweat, so the perfume department is not the plumbing department. Some deodorants also target odor causing bacteria or contain powders that absorb moisture. Antiperspirants reduce how much you sweat. Check for the word "antiperspirant" on the packaging and an aluminum active ingredient, such as aluminum chloride, aluminum chlorohydrate or aluminum zirconium.17

Underarm odor needs attention where it starts, not a product rollout across every available inch. A whole body deodorant does not reduce sweating unless it contains an antiperspirant ingredient. Applying deodorant to places without odor will not reduce the underarm smell, and whole body products can irritate sensitive areas.7

When should you get help?

Book a medical appointment if self care has not helped and the odor affects your confidence, the usual smell changes, or you suddenly sweat much more than before. New odor unrelated to hygiene, especially odor also affecting your breath or urine, deserves assessment. Odor alone cannot identify the cause.56

Sweating at rest or in cold temperatures can be a feature of hyperhidrosis, meaning excessive sweating beyond what your body needs for cooling. A clinician can assess whether medication or another condition contributes. If ordinary antiperspirants are not enough, a pharmacist can discuss stronger options, and a doctor can prescribe treatment. Persistent odor sometimes needs treatment for a skin infection rather than more deodorant.456