At what age can one begin using deodorant?

Puberty generally occurs around age 11 in girls and between ages 12 and 13 in boys, although these benchmarks can vary among individuals.

Puberty marks the gradual transformation of a child’s body into that of an adult. This period, which lasts on average five years, is triggered by a progressive rise in sex hormones, particularly androgens in boys and estrogens in girls. One of the signs of this transition is the emergence of body odors associated with sweating. If infants and young children already sweat, their perspiration is odorless. This change at puberty is primarily due to the activation of a new type of sweat gland. The human body actually has two types of sweat glands:

• The eccrine glands, present from birth, produce sweat composed mainly of water and mineral salts. Their function is primarily thermoregulatory, allowing heat to be released to maintain a stable body temperature.

• The apocrine glands, on the other hand, are primarily located in the armpits, groin, and chest. They remain inactive during childhood and only become active at puberty under the influence of sex hormones.

Sweat produced by apocrine glands is thicker and richer in lipids, proteins, and organic compounds. This specific composition makes it an ideal substrate for bacteria present on the skin surface. By feeding on these molecules, these microorganisms produce volatile odorant compounds, particularly fatty acids, which are responsible for unpleasant sweat odors. This phenomenon is also linked to changes in the skin microbiota during adolescence. Before puberty, the latter is characterized by high bacterial diversity, with a predominance of bacteria of the genus Bacillus. This richness gradually decreases as sebaceous glands become more active under the influence of sex hormones. The skin becomes enriched in lipids, which favors the colonization by lipophilic microorganisms, such as Cutibacterium and the fungus Malassezia.

Furthermore, the emergence of body hair, under the control of sex hormones—particularly androgens—accentuates bacterial proliferation and the production of unpleasant odors. Indeed, hair, especially in the underarm region, creates a warm, humid, and poorly ventilated environment, conducive to microbial growth. It also traps sweat, extending its contact time with the skin and thereby intensifying odors.

In short, the main factors responsible for the emergence of unpleasant odors are:

• The activation of apocrine glands by sex hormones, producing a richer sweat.

• Evolution of the cutaneous microbiota and the predominance of lipophilic microorganisms.

• The emergence of hair, which promotes the development of microorganisms.

Several studies have highlighted increased sweating during adolescence. Notably, one study published in Medicine & Science in Sports & Exercise examined eccrine sweat gland responses to exercise in boys at different stages of pubertal maturity. To this end, three groups of prepubertal, midpubertal, and postpubertal adolescents were exposed to two consecutive bouts of moderate exercise to stimulate sweating. The results show that overall sweat rate increases as puberty progresses, rising from 4.95 mL·min⁻¹·m⁻² in prepubertal children to 6.70 mL·min⁻¹·m⁻² in postpubertal adolescents.