Body odour is the smell caused by bacteria feeding on sweat on the skin, especially in the armpit and groin area. It is often called 'BO'.
Sweat itself doesn't smell. The smell is made by the bacteria that feed on this sweat, which comes from the apocrine glands in the armpits and groin area. The sweat from these glands contains proteins and fats, which bacteria can feed on.
Sweat produced from the rest of the body is made by different glands called eccrine glands. It is saltier, and does not encourage the growth of bacteria and therefore doesn't smell.
Sweaty feet may smell unpleasant because we wear shoes and socks. The warm, enclosed environment is ideal for bacteria and fungi to grow.
Sweating helps the body to control its temperature. On average we lose over a litre of sweat a day.
Excessive sweating and body odour are more likely if people are overweight, exercising, anxious, or have certain medical conditions such as thyroid disease.
Hot weather encourages more sweating, and eating certain foods such as onions, fish, garlic, and spicy foods may cause the sweat to smell more strongly.
At puberty, our bodies begin to make more of the hormone testosterone. This makes the apocrine glands produce more sweat, which is why sweating and body odour are more common after puberty.
Not washing, and wearing unwashed clothes, allows bacteria to build up
You should have regular baths or showers. You should wear clean clothes; these should be washed and then dried quickly, as bacteria can survive in damp clothing. Wash and thoroughly dry your feet regularly. Wear open sandals or bare feet where possible. When you wear enclosed shoes use cotton socks and avoid wearing trainers too often.
After washing, use an under-arm deodorant containing an anti-perspirant. This will reduce the amount of sweat produced. Different brands have different active ingredients so some may work better than others.
You can also get the following preparations from pharmacies (chemists):
chlorhexidine: an antibacterial solution used to wash feet and under the arms, and kills the bacteria that cause BO, and anhydrol forte: it blocks sweat glands, and can be applied at night a couple of times a week. Avoiding very spicy foods may also help.
There are surgical treatments, but only for very severe sweating - a condition known as hyperhidrosis. This involves either:
removing a small area of skin from the armpit, to remove some sweat glands (under a local anaesthetic), or destroying the nerve centres that control sweating under the arms. This is called an endoscopic transthoracic sympathectomy, and is done under a general anaesthetic. Botox (a bacterial poison that stops nerves from working properly) can also be used as a treatment for hyperhidrosis. A small amount of Botox is injected into the skin near the armpit.
This helps with sweating from the armpit but does not help with excessive sweating of hands and feet. It is a safe but temporary solution, lasting a few weeks.
Copied from the NHS Direct website