Armpits smell because sweat, produced by apocrine sweat glands located in the armpits, interacts with bacteria on the skin. This interaction creates a byproduct with an unpleasant odor.
The Science Behind the Smell
Our bodies have two types of sweat glands: eccrine and apocrine. Apocrine glands, found in areas like the armpits, produce a thicker sweat that contains proteins and lipids. When this sweat mixes with bacteria naturally present on the skin's surface, it leads to the production of thioalcohols. These volatile molecules evaporate, creating the characteristic armpit odor. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
- Sweat: The apocrine sweat itself doesn't smell initially. The odor comes from the bacterial breakdown of its components.
- Bacteria: Different types of bacteria thrive in the warm, moist environment of the armpits, contributing to the smell's intensity and variability. Even after washing, some bacteria remain, potentially leading to lingering odor. [8]
- Genetics: Genetic factors can play a role; a non-functional ABCC11 gene, for example, can impact the ability of sweat molecules to reach the armpit surface, influencing bacterial interaction and odor. [5]
Reducing Armpit Odor
While some odor is unavoidable, several practices can minimize it:
- Regular washing: Thorough washing of the armpits twice daily helps reduce bacteria. [9]
- Drying: Ensuring armpits are completely dry after washing prevents bacteria from thriving. [9]
- Deodorants and Antiperspirants: Deodorants mask odors, while antiperspirants reduce sweat production, limiting bacterial interaction. [2, 9]
- Shaving: Regular shaving can reduce bacteria buildup, especially in hairy armpits. [9]
References:
- Your skin contains eccrine and apocrine sweat glands. The latter open into hair follicles and can be found in the armpits. When sweat comes in contact with bacteria, a smell is produced. Sometimes that smell is less-than-desirable.
- Healthline: Smelly Armpits: Causes, Treatments, Prevention, and More. https://www.healthline.com/health/smelly-armpits
- Cleveland Clinic: Body Odor: Causes, Changes, Underlying Diseases & Treatment. https://my.clevelandclinic.org/health/symptoms/17865-body-odor
- NPR: Meet The Bacteria That Make A Stink In Your Pits. https://www.npr.org/sections/health-shots/2015/03/31/396573607/meet-the-bacteria-that-make-a-stink-in-your-pits
- ASM: Microbial Origins of Body Odor. https://asm.org:443/Articles/2021/December/Microbial-Origins-of-Body-Odor
- Medical News Today: Smelly armpits: Causes, treatment, prevention, and when to seek help. https://www.medicalnewstoday.com/articles/smelly-armpits
- Harley Street Health Centre Blog: Are smelly armpits a sign of illness? https://www.harleyhealthcentre.com/blog/general-health/general-healthsmelly-armpits-sign-serious-illness-see-doctor
- Degree: Armpits Still Smelly After Washing? Discover Solutions. https://www.degreedeodorant.com/us/sweat-zone/armpits-smell-after-shower/
- NHS: Body odour. https://www.nhs.uk/conditions/body-odour-bo/
- Arm & Hammer: Why Do My Armpits Smell So Bad? https://www.armandhammer.com/en/articles/why-do-armpits-smell-bad
