Key Takeaways

Sweating under the breasts is normal and triggered by heat and activity.
Under-breast sweat builds up because skin touches skin with little airflow, so sweat can't evaporate.
A bra traps heat and moisture in the under-boob area all day.
A breathable, well-fitting bra, the right fabrics, and a whole body deodorant can all help.
If you have a sore, red rash in the fold, it’s best to see your doctor.

UNDER-BREAST SWEAT: WHY IT HAPPENS AND HOW TO MANAGE IT

Sweat under the breast is common, especially when you're active or the weather is warm. It happens because skin is touching skin under the bust with very little airflow, so sweat builds up there instead of evaporating. A bra adds to this by trapping heat and moisture all day.

But under-boob sweat is manageable. A well-fitting, breathable bra, the right fabric choices, and a whole body deodorant can all help.

WHY DOES UNDER-BREAST SWEAT HAPPEN?

You have sweat glands all over your body, including under your breasts. “Only about 1-2% of sweat is produced in the underarm; the rest is distributed across the body,” explains Unilever R&D scientist Matt Annecharico.

When heat, friction, and zero airflow meet, that's when sweat production kicks into high gear. "Sweat in areas not exposed to the air, or under heavy clothes, evaporates at a much slower rate and this can be uncomfortable."

A bra adds to the problem, since the band, underwire, and padding all sit against the fold.

Hormonal changes, such as those around your cycle or menopause, can also affect how much you sweat,¹ and let's not forget the role of genetics. Some women just sweat more than others.

WHY DOES UNDER-BREAST SWEAT SMELL?

Sweat is mostly odorless when it reaches the surface of your skin. Odor starts when skin bacteria get to work on it, and the fold under your breast creates the perfect environment for them to thrive and multiply.² It's an area that's warm, damp and trapped under your bra and clothes so air can’t circulate. That’s why it can smell stronger than skin that gets airflow.

Breast size also matters because of more skin-on-skin contact and deeper folds if your breasts are on the larger side.

If the odor is bad, or there's a rash, pus-filled bumps, or raw skin, there could be an infection going on. See your doctor if you notice any of these signs.³

HOW TO MANAGE UNDER-BREAST SWEAT

Sweat and odor in this area are normal and not a hygiene failure. Here are some easy solutions and what you can put under your breasts for sweating:

Shower or bath daily. Cleanse the fold with a gentle body wash and rinse thoroughly.
Dry the area thoroughly. Pat dry rather than rub, and you could even use a hair dryer on a cool setting.
Tackle odor. A whole body deodorant is your best defense against under-boob odor. Look for one that's aluminum-free, dermatologist tested and offers up to 72 hours of odor protection. Apply to clean, dry skin before dressing. Patch test first and always check the label to see where you can apply it. Avoid if you have a rash or broken, raw skin.
Get the bra right. Choose a well-fitting, supportive bra in a breathable fabric. If you wear a sports bra, consider removing the padding, as it traps moisture.
Choose fabrics intentionally. Loose, breathable fabrics for everyday wear and moisture-wicking fabrics for workouts. Change out of a damp bra as soon as you can.
Add a liner. A bra liner in the fold can help absorb moisture.

SWEAT RASH UNDER THE BREASTS

Constant moisture and rubbing can irritate the skin in your folds. If you notice a red or reddish-brown rash that itches, stings, or burns, it could be intertrigo, which happens when skin rubs against skin in a warm, damp area. The area beneath the breasts is a common spot.³

Heat rash, also called sweat rash, is a different thing. It happens when sweat gets trapped in the skin, and in adults it tends to show up in skin folds and where clothing rubs.⁴ It can itch too.

In brown and Black skin, heat rash can leave temporary lighter or darker patches that usually fade within weeks to months.⁴ Keep the area clean, cool, and dry.

WHEN SHOULD YOU SEE A DOCTOR?

Most under-breast sweat is nothing to worry about, but here are some symptoms that should be checked out:

A rash under your breasts that doesn’t improve within a few days or gets worse
A foul smell, pus, raised tender bumps, or raw, cracked skin
Sweating that starts suddenly or increases without explanation
Sweating that disrupts your daily routine⁵
Unexplained night sweats⁵

Seek immediate care for: Heavy sweating with dizziness, chest pain, or pain in the throat, jaw, arms, or shoulders.⁵

You can’t stop sweating under your breasts, as sweating is how your body cools itself down. To prevent moisture from building up, wear a well-fitting, breathable bra, keep the area dry, change out of a damp bra and clothing quickly, and use a whole-body deodorant to keep odor in check.

Looking for a deodorant for boob sweat odor? Degree Whole Body Deodorants are designed for odor control beyond the underarms, with up to 72 hours of odor protection. Always check the label to see where you can use a formula.

It's more about reducing sweat build-up than preventing it because under-boob sweat will still happen. Apply whole body deodorant to clean, dry skin to keep odor at bay, wear a moisture-wicking sports bra, and consider removing the padding.

A red or reddish-brown rash in the fold that itches, stings or burns may be intertrigo, which happens when skin rubs against skin in a warm, damp area. Keep it clean, cool, and dry. If it doesn't improve within a few days, worsens, or develops a foul smell or pus, see a doctor.

Under-breast sweat is a normal part of how your body cools itself, and it says nothing about your hygiene. A breathable, well-fitting bra, the right fabrics, thorough drying, and a whole body deodorant for odor all make it easier to manage, so you can get on with your day feeling fresh and comfortable.