Heat makes people sweat and when this occurs in confined spaces, we become acutely conscious of body odour, usually that of people nearby. Body odour comes mostly from sweat, which is why it is less of an issue during winter months.

Everyone sweats; the amount you sweat doesn’t necessarily impact your body odour, nor is it proportional. A person can have an unpleasant body odour but not be sweaty. Conversely, a person can sweat excessively but still not smell.

Body odour is a product of the action of bacteria living on your skin and how
it acts on your sweat. The species of bacteria living on your skin depends on your genes, environment and diet. People who live together or are related by blood often share bacteria and have similar body odours.

Sweat is produced in sweat glands. We have two types of sweat glands — eccrine and apocrine. Eccrine glands are found all over the body, including the palms and soles of the feet. Their function is to produce clear sweat to cool the body.

When the temperature is high, our body gets covered in sweat while doing physical activities. As this evaporates, the body cools down. Heat stroke is prevented. Cooling is efficient when the environment is dry, there is air circulation and the clothes worn are made of natural or artificial fibres that wick away the sweat.

Apocrine glands are found in the armpits and the genital area. After puberty, they mature and start functioning. They produce a more fatty, waxy sweat. As these areas are also hairy, the sweat gets trapped. Bacteria live on hair shafts. They break down the sweat, which releases an unpleasant odour.

Our food gets digested in the intestine and circulates through the blood. It can release compounds through sweat that can cause an unpleasant smell. Foods like broccoli, cauliflower, garlic and onions are well-known offenders. Spices like cumin and fenugreek also cause this problem. That is because they break down to form sulphur compounds. If these are combined with capsaicin-containing chillies and green peppers, the sweating and odour increase.

Alcohol increases sweating. The aromatic chemicals in the alcohol, along with the odours of the snacks consumed at the same time, are released in the sweat.

Smokers and those who chew tobacco absorb nicotine and other chemicals through the lungs and buccal mucosa into their bloodstream. These reach the sweat glands, where they turn the sweat yellow and the smell rancid. Tobacco also causes tooth decay and bad oral hygiene. Halitosis (bad breath) adds to the repulsive body odour.

The writer has a family practice at Vellore and is the author of Staying Healthy in Modern India. If you have any question on health issues please write to yourhealthgm@yahoo.co.in