Why odour settles in the armpit of a top
Short answer: The armpit has the glands that release fatty sweat, the skin is warm and enclosed, and the fabric sits close. Every condition for odour is therefore found in the same small area. That explains why the smell settles right there in the top, even when the rest of the garment feels clean.
A small area with many conditions
The armpit is one of the places on the body where several things meet at once. The skin is warm, the area is enclosed, and the fabric sits tight against the body all day. It is no coincidence that odour almost always settles in exactly that part of the top and not on the sleeves.
The glands are different
Besides the ordinary sweat glands, the armpit has glands that release a fatty fluid. The fluid barely smells when it comes out, but it is the best food bacteria can get. The odour only appears once bacteria start working on it, so the problem is not in the sweat itself.
The area is enclosed
Under the arm there is hardly any air movement or evaporation, and the arm rests close to the body for most of the day. The moisture therefore stays in the fabric for hours instead of disappearing. The longer it stays, the better conditions the bacteria have. See also all bamboo socks for women.
The fabric sits close
A close-fitting top presses the fabric directly against the skin under the arm. Sweat, fat and warmth then move into the fibre instead of letting air pass through. A looser cut lets in a little more air, but the fat still reaches the fabric. It depends more on the area than on how nice the top is.
Bacteria live on the fat
Bacteria on the skin are perfectly normal and harmless, but they turn the fatty substances into compounds that smell. In a warm, enclosed armpit this happens quickly, and with close fabric some bacteria move into the material. There they keep finding food, even after you have taken the top off.
Why the smell stays
Fatty substances bind to the fibre and are not rinsed out at a low temperature. That is why a clean garment can smell again as soon as it warms up on the body. The heat wakes the residues up. See Turiform and bamboo tennis socks for women for textiles that are also washed often.
Fat residues build up
Each time a top is washed at a low temperature, a small part of the fat stays behind in the fibre. After many washes there is a layer that does not come loose from one wash to the next. That is why it often smells worse after a while, even though you wash as often as before.
Temperature and detergent
The detergent has to loosen the fat, and it works best when the water is warm enough. A detergent with enzymes helps, because enzymes break down fat and protein. Always check the care label first, since not every fabric tolerates a higher temperature. If in doubt, choose a longer programme rather than a short one.
How to limit the smell day to day
Hang the top to air when you take it off, and do not leave it crumpled in a basket. Wash it before the fat has had time to settle. A little vinegar in the water can help with clothes that already smell. These are small habits, and they matter most when repeated every week.
Frequently asked questions
How do I get the smell out
Soak the garment in water with a little vinegar, or use a detergent with enzymes. Then wash as warm as the care label allows, and preferably choose a longer programme so the fat has time to loosen from the fibre.
Does a higher temperature help
Yes, but only if the fabric tolerates it, which you can see on the care label in the garment. If it cannot take more heat, a longer programme and a detergent with enzymes can give part of the same effect.
Why does it smell worse after a while
Because fat residues build up in the fibre, wash after wash. The layer grows slowly, and eventually a low temperature can no longer keep up. Washing warmer helps if the label allows it, and so does letting clothes dry fully.
You can find the full range at Bamboo-Clothing.com.
