The million apocrine glands that form the rest of the sweat glands are located in the axilla and the urogenital region. These glands produce a colourless fluid that has proteins and fats. The bacteria present in the skin, especially in the hairy flexures like the armpit, act upon the sweat of the apocrine glands breaking it down into end products with a characteristic odour. Unlike the eccrine glands, the apocrine glands develop and function only around puberty under the influence of the sex hormones. Therefore the sweat of children is generally odourless. However, there are a few conditions when the child's sweat may be offensive. Sometimes children attain precocious puberty when the apocrine glands become active under the influence of the prematurely circulating sex hormones.
In a rare genetic condition known as 'Fish Odour Syndrome' the lack of a particular hormone interferes with protein metabolism and results in the accumulation of trimethylamine, a compound with an offensive fishy smell, rather like Caliban, the social outcast in Shakespeare's Tempest.If a child's sweat has a persistently offensive odour despite reasonable standards of personal hygiene it might be advisable to seek medical advice and further investigation.