Why Does Body Odour Get Worse in the Summer?

After the arduous pelting of winter snow, and the relentless showers of spring, the summer vibes are indeed welcome. There’s so much to love about summer, after all. Like the sunny skies, the blanketing warmth, feeling the sun on our faces… But then our noses are assaulted by the acrid stink of body odour. If that wasn’t bad enough, the summer heat and humidity feel like an amplification hex. So, what gives? Is this something that can be worked on, or rooted in hopelessly natural processes? Read on to discover the true depth of sweat, and hopefully some tips to take home.

 

Check out Key Takeaways at the end for a quick summary

Is Sweat Really Odourless?

Despite contrary belief, no, that stinky smell isn’t the sweat talking. At least, not on its own. Then you might ask, okay, what is sweat, and what does it do? Well, sweat is primarily known to be excreted by three main types of sweat glands: eccrine, apocrine, and apoeccrine, though this article will focus on the former two, as apoeccrine is not yet well-researched (Baker, 2019). These sweat glands have different purposes, and excrete different types of sweat. 

Eccrine is the smallest of the three, but most plentiful in the human body, found basically everywhere from the palms and soles, to the face, trunk, and limbs (Baker, 2019). The sweat excreted by this sweat gland is mostly water (99%) and salt (sodium chloride), along with smaller amounts of other chemicals (Kanlayavattanakul & Lourith, 2011). Its main purpose in the human body is thermoregulation, meaning it helps you cool off if temperature rises (Baker, 2019). Maybe next time you take a run on a hot, summer day, you’ll thank your eccrine glands for keeping you cooler by upwards of 50% (Casa et al., 2019).

Apocrine glands open into hair follicles as opposed to the skin surface like eccrine, and can be found in places such as the armpits, chest, face and perineum (Baker, 2019). These glands have been observed to be dormant (i.e. don’t participate in sweat secretion) till puberty, though they are present at birth (Baker, 2019). Sweat produced by this gland is described as “viscous, lipid-rich sweat”, full of “proteins, sugars and ammonia” (Baker, 2019). Research suggests that the role of this sweat is to produce pheromones (body odour), though this is less useful for humans (Baker, 2019). Note that this doesn’t mean the sweat produced by apocrine glands itself is responsible for the smell.

Sweat alone doesn’t smell. For example, a 2011 review published in the International Journal of Cosmetic Science explains that sweat from both eccrine and apocrine glands is odourless until bacteria, such as Corynebacterium and Staphylococcus species break it down into smelly compounds, a major contributor to underarm odour (Kanlayavattanakul & Lourith, 2011). In summer, the heat and humidity create a perfect environment for these bacteria to thrive, leading to more pronounced odours. 

 

The Role of Bacteria and Sebum in Creating Body Odour

Bacteria are the primary drivers of body odour, but sebum, an oily substance produced by sebaceous glands, also plays a supporting role. The skin hosts a diverse microbiome, including bacteria like Corynebacterium and Staphylococcus, which catabolize components of sweat and sebum to produce smelly compounds (Kanlayavattanakul & Lourith, 2011). Apocrine sweat is particularly appealing to these bacteria. When they break down these molecules, they produce volatile fatty acids, which have strong, unpleasant odours.

Sebum, secreted by sebaceous glands found across the body but concentrated in areas like the face and scalp, contributes by providing a lipid-rich environment that supports bacterial growth. While sebum itself is largely odourless, it can be broken down by bacteria into odorous compounds, particularly in areas with both sweat and sebaceous glands, like the armpits. Sebum also provides moisture and nutrients that enhance bacterial activity, indirectly contributing to body odour (Kanlayavattanakul & Lourith, 2011).

However, perhaps you’ve already heard of the ABCC11 gene. If you’ve ever wondered why some people just don’t smell putrid after sweating buckets (and maybe that’s you) it’s because these individuals have a “dysfunctional ABCC11 gene” (Martin et al., 2010). Research suggests that non-functional ABCC11 genes in people leads to near-never secretion of amino acid conjugates, which leads to the “nearly complete loss” of common odour components in armpit sweat (Martin et al., 2010). This gene is also in charge of determining your earwax type, so if your earwax is dry, then personal body odour will likely be lower on your list of summer irritations.

 

Armpit Sweat vs. Foot Sweat – Different Causes

Not all body odours are the same, and the differences between armpit and foot sweat highlight why. Armpit odour is primarily driven by apocrine glands, which produce a nutrient-rich sweat that bacteria like Corynebacterium metabolize into pungent compounds. The armpit’s warm, moist environment, often exacerbated by hair that traps sweat and bacteria, makes it a hotspot for strong odours. Research from the Journal of Investigative Dermatology indicates that Corynebacterium species are particularly efficient at producing odourous acids in the axilla (armpits), contributing to the characteristic underarm smell (Martin et al., 2010).

Foot odour, on the other hand, stems from eccrine glands, which produce a watery sweat composed mainly of water and salt. The feet lack apocrine glands, so the odour is caused by bacteria breaking down sweat and dead skin cells in the moist, enclosed environment of shoes and socks. Foot odour, often described as cheese-like, results from the isovaleric acid produced by certain bacteria. For example, Staphylococcus epidermidis on the skin metabolizes amino acids like leucine from sweat, leading to the creation of isovaleric acid (Ara et al., 2006). The confined, warm conditions in footwear create an ideal setting for bacterial growth, especially in summer when feet sweat more. 

These differences in gland types and environments explain why armpit odour is often sharper and more pungent, while foot odour can be milder but still noticeable, particularly in poorly ventilated shoes. 

 

Deodorant vs. Antiperspirant – What’s the Difference?

When tackling body odour, many turn to deodorants or antiperspirants, but these products serve distinct purposes. Deodorants work by masking or neutralizing odour, often through antibacterial agents that reduce the number of odour-causing bacteria or fragrances that cover up smells. They don’t affect sweat production, focusing instead on the odour itself. Antiperspirants, conversely, reduce sweating by using metal-salt compounds to temporarily block sweat pores, limiting the amount of sweat available for bacteria to break down. Many products combine both functions for comprehensive odour control (Mayo Clinic, 2025).

Antiperspirants containing metal salts reduce sweat produced, while deodorants often use alcohol to create an acidic environment that is less hospitable to bacteria (Mayo Clinic, 2025). Choosing between them depends on your needs: antiperspirants are ideal for heavy sweaters, while deodorants suit those with minimal sweat but persistent odour. For summer, when sweating is more intense, a combination product might offer the best protection.

 

Everyday Habits That Help Reduce Body Odour

Managing body odour, especially in the summer, involves more than just applying products. Here are practical habits to keep odour at bay, supported by expert recommendations: 

1. Shower regularly: Washing with soap, particularly antibacterial soap, removes bacteria and sweat from the skin. (WebMD, 2025)
2. Dry Thoroughly: Bacteria thrive in moist environments, so drying completely after showering is crucial. Keeping skin dry makes it harder for bacteria to multiply. 
3. Wear Breathable Fabrics: Clothing made from natural fibers like cotton allows sweat to evaporate, reducing moisture for bacterial growth. Harvard Health emphasizes the importance of breathable materials (Watson, 2024). 
4. Change Clothes Daily: Underwear, socks, and other garments can harbor bacteria and sweat, so daily changes are essential, especially in summer.
5. Use Antiperspirant or Deodorant: Apply to clean, dry skin for maximum effectiveness. Applying antiperspirant at night can enhance its sweat-blocking action.
6. Shave Armpits: Hair traps sweat and bacteria, increasing odour. Shaving can reduce this, particularly in the armpits.
7. Watch Your Diet: Foods like garlic, onions, and spicy dishes can influence body odour. WebMD notes that these foods can be carried in sweat, contributing to odour (WebMD, 2025). A balanced diet rich in whole foods, as suggested by Harvard Health, can also support overall health and potentially reduce odour indirectly (Harvard Health, 2024). 
8. Stay Hydrated: Drinking water dilutes sweat, potentially reducing its concentration and odour.
9. Manage Stress: Stress triggers apocrine gland sweating, which is more odour-prone. Relaxation techniques like meditation can help. Check out how to manage stress-induced fatigue.
10. Consider chlorophyllin: Chlorophyllin, a derivative of the green plant pigment chlorophyll, is sometimes suggested as an "internal deodorant" (Young et al., 1980). The theoretical idea is that it might help by neutralizing odour-causing compounds or possessing antioxidant properties (Cleveland Clinic, 2025). While some claims suggest antimicrobial effects, a key study on chlorophyllin for body odour explicitly stated that its "Bacteriologic studies failed to confirm reports in the literature of antibacterial properties for chlorophyllin" (Young et al., 1980). Robust scientific evidence directly supporting its widespread effectiveness for general body odour when taken orally is limited, with many positive studies being older or small-scale (Cleveland Clinic, 2025). For instance, a 1980 study on geriatric patients found it helpful for body and fecal odours (Young et al., 1980). However, authoritative sources indicate "no good scientific evidence" for its general use (WebMD). Chlorophyllin is generally considered possibly safe for short-term use (up to 3 months) (WebMD), but potential side effects include mild stomach upset (Cleveland Clinic, 2025), discolored stool (Cleveland Clinic, 2025), and increased sun sensitivity (WebMD). As with any supplement, you should always consult a healthcare provider before starting any new regimen (Medical News Today, 2025).

 

Sources/Further Reading

1. Ara, K., Hama, M., Akiba, S., Koike, K., Okisaka, K., Hagura, T., Kamiya, T., & Tomita, F. (2006). Foot odor due to microbial metabolism and its control. Canadian Journal of Microbiology, 52(4), 357–364. https://doi.org/10.1139/w05-130
2. Baker, L. B. (2019). Physiology of Sweat Gland function: the Roles of Sweating and Sweat Composition in Human Health. Temperature, 6(3), 211–259. https://doi.org/10.1080/23328940.2019.1632145
3. Berry, J. (2025, April 29). Proven benefits of chlorophyll and how to consume more (J. Meacham, Ed.). Www.medicalnewstoday.com. https://www.medicalnewstoday.com/articles/322361
4. Casa, D. J., Cheuvront, S. N., Galloway, S. D., & Shirreffs, S. M. (2019). Fluid Needs for Training, Competition, and Recovery in Track-and-Field Athletes. International Journal of Sport Nutrition and Exercise Metabolism, 29(2), 175–180. https://doi.org/10.1123/ijsnem.2018-0374
5. CHLOROPHYLLIN: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews. (n.d.). Www.webmd.com. https://www.webmd.com/vitamins/ai/ingredientmono-626/chlorophyllin
6. Cleveland Clinic. (2021, November 23). Are There Health Benefits to Using Liquid Chlorophyll? Cleveland Clinic. https://health.clevelandclinic.org/are-there-health-benefits-to-using-liquid-chlorophyll
7. Kanlayavattanakul, M., & Lourith, N. (2011). Body malodours and their topical treatment agents. International Journal of Cosmetic Science, 33(4), 298–311. https://doi.org/10.1111/j.1468-2494.2011.00649.x
8. Martin, A., Saathoff, M., Kuhn, F., Max, H., Terstegen, L., & Natsch, A. (2010). A functional ABCC11 allele is essential in the biochemical formation of human axillary odor. The Journal of Investigative Dermatology, 130(2), 529–540. https://doi.org/10.1038/jid.2009.254
9. Mayo Clinic. (2025, May 3). Sweating and body odor - Diagnosis and treatment - Mayo Clinic. Www.mayoclinic.org. https://www.mayoclinic.org/diseases-conditions/sweating-and-body-odor/diagnosis-treatment/drc-20353898
10. Watson, S. (2024, July 24). What’s that smell? Get rid of body odor. Harvard Health. https://www.health.harvard.edu/staying-healthy/whats-that-smell-common-and-less-common-causes-of-body-odor
11. WebMD. (2025, February 1). 6 Tips for Reducing Body Odor (D. Brennan, Ed.). WebMD. https://www.webmd.com/skin-problems-and-treatments/reduce-body-odor
12. Young, R. W., & Beregi, J. S. (1980). Use of Chlorophyllin in the Care of Geriatric Patients. Journal of the American Geriatrics Society, 28(1), 46–47. https://doi.org/10.1111/j.1532-5415.1980.tb00124.x