How can medicines alter our body odour?

The body odour is not produced by sweat, which is initially odourless.

It results from the encounter, at the surface of the epidermis, between the secretions of the sweat glands and the skin microbiome. The eccrine glands, distributed across the entire body, release mainly water and salts, whereas the apocrine glands, located in hair-bearing areas, secrete denser organic compounds such as lipids and proteins. By metabolising these substances, the bacteria that reside on our skin release odorous volatile compounds. This process is known as bromhidrosis.

Body odours also depend on external factors, in particular on what we ingest via our diet.

When we ingest a food, it is normally metabolised by the liver before being eliminated. However, if certain residues are not completely broken down, they are transported by the bloodstream to the sweat glands. Once excreted through the pores, these metabolites modify the chemical composition of sweat or alter the bacterial ecosystem of the skin, thereby changing—sometimes subtly, sometimes markedly—the odour emitted by the body.

The majority of odour changes linked to taking medication are not due to the drug itself, but to its ability to stimulate the production of sweat.

Certain active substances interfere with the autonomic nervous system, which regulates our automatic functions, including body temperature. By sending an incorrect signal to the sweat glands, these medicines trigger profuse sweating even when the body does not need to cool down. This increased presence of water and nutrients on the skin’s surface provides a favourable environment for bacteria. The more material the bacteria have to break down, the more odorous volatile compounds are released, thereby intensifying the natural scent.

This phenomenon of excessive sweating is frequently observed with antidepressants and anxiolytics. These treatments alter the concentration of neurotransmitters, such as serotonin or noradrenaline, which are involved in thermoregulation in the brain. By disrupting this internal thermostat, they trigger night sweats or hot flushes. This effect is also seen with certain hormone therapies or with medicines used to treat high blood pressure, such as captopril or enalapril, which can dilate blood vessels and indirectly stimulate the skin’s glands.

This list is not exhaustive: zidovudine, tramadol, pregabalin, tamoxifen, codeine, bupropion hydrochloride and paroxetine mesilate may also increase perspiration.

More rarely, certain medicines alter the “chemical signature” of our secretions. Once ingested, the medicine is broken down by the liver into smaller molecules called metabolites. If these residues have a strong odour and are not completely eliminated by the kidneys, they are expelled through the pores. This is the case with certain antibiotics, notably penicillin, whose sulphur-containing molecules are carried by the blood to the apocrine glands. The sweat then acquires a characteristic smell, often described as acidic or chemical.

Finally, certain treatments alter the balance of the skin microbiome. By eliminating some of the “good” bacteria in favour of other, more odour-producing species, medicines such as broad-spectrum antibiotics can durably transform body odour. In this case, the change does not arise from within the body, but from the modification of the living ecosystem at its surface. This imbalance, although temporary, often requires particular attention to hygiene and to the choice of cleansing products that respect physiological pH, in order to restore a healthy skin flora.

If you notice a persistent and/or troublesome change in your body odour after starting a new treatment, do not hesitate to seek advice from your GP.

• LAZAREVIC V. & al. Mapping axillary microbiota responsible for body odours using a culture-independent approach. Microbiome (2015).

• DOTY R. L. & al. Impact of antibiotics on smell dysfunction. World Journal of Otorhinolaryngology - Head and Neck Surgery (2018).

• BAKER L. B. Physiology of sweat gland function: The roles of sweating and sweat composition in human health. Temperature (2019).

• SMEETS M. & al. Intrinsic and extrinsic factors affecting axillary odor variation: A comprehensive review. Physiology and Behavior (2023).