The sweat glands in the underarms remain undeveloped until puberty, so body odor does not generally occur in children. However, there may be a variety of conditions that can cause underarm odor in children. If frequent bathing does not resolve a child's underarm odor, parents should contact their child's pediatrician to investigate the underlying cause.
Children who consume smelly foods, such as garlic, onions or curry, may develop body odor when these strong-smelling foods seep through their pores. In some cases, the hormones used in milk may contribute to an unpleasant underarm smell in some children. Avoiding fatty, oily foods or feeding your child only hormone-free organic milk may eliminate the problem.
Ketones, a chemical that the body excretes when breaking down fat for energy, can cause a sweet-swelling underarm and body odor. Diabetes, a metabolic disorder that makes it difficult for the body to break down sugar from carbohydrates for energy, can cause a child to excrete ketones in the urine and sweat. Children whose sweat or breath smells fruity or sweet should be examined by a doctor and tested for diabetes.
Children with phenylketonuria (PKU), a disorder that causes phenylalanine to build up in the blood, may experience an unpleasant underarm and body odor, according to Merck Manuals. Routine screening tests usually detect PKU at birth, and as long as a child consumes a diet free of phenylalanine, he will have a normal smell. A phenylalanine-restricted diet involves avoiding meat, milk and other foods that contain protein. However, if a young child with PKU begins eating foods with phenylalanine, he may develop a mousy body smell. This odor results because the body cannot process the phenylalanine and excretes it in the child's sweat and urine.
When children develop physical and hormonal signs of puberty at an early age, parents may notice underarm odor. When a child enters puberty, the hormones stimulate glands in the skin, including those in the armpits. When bacteria on the skin mixes with sweat, the result is an unpleasant odor, even in young kids. Body odor isn't the only problem -- maturing too early can lead to shorter adult height and emotional strain and embarrassment due to breast development and early periods in girls or increased sexual libido in boys. According to eMedicineHealth, doctors usually use medications to treat children with precocious puberty.
A condition called hyperhidrosis could contribute to underarm odor in children. Hyperhidrosis is caused by overactive sweat glands, and the International Hyperhidrosis Society estimates that 9 million people in the United States, including many children and teens, experience the condition. For children with hyperhidrosis, doctors may use prescription-strength antiperspirants or injections to reduce the excess sweating.