Common Causes (Ranked by Likelihood)
Brevibacterium linens is the dominant cause of the cheesy foot smell. It metabolizes the amino acid methionine (from dead skin cells and sweat) into methanethiol — a volatile sulfur compound with a sharp, cheesy, parmesan-like smell. This same bacterium is used to produce the rinds and distinctive smells of limburger, munster, Port Salut, and other washed-rind cheeses. The bacterium requires moist, warm, slightly alkaline conditions — exactly what sweaty feet in shoes provide. People with hyperhidrosis (excessive sweating) or those who wear occlusive shoes have far more Brevibacterium activity.
Staphylococcus epidermidis bacteria produce isovaleric acid from the amino acid leucine in sweat. Isovaleric acid smells like sweaty socks or parmesan — it's the same compound that gives parmesan cheese part of its flavor profile. Both Brevibacterium and S. epidermidis are often present simultaneously, and their combined products create the full range of cheesy foot odor. S. epidermidis is part of the normal skin flora but proliferates dramatically in warm, moist conditions.
Athlete's foot (tinea pedis) caused by Trichophyton fungi produces a different type of cheese-like or musty smell alongside bacterial odor. The fungal infection creates skin breakdown between toes (maceration) which provides more substrate for bacteria and produces its own organic acids. Many people have both a bacterial overgrowth and a fungal infection simultaneously — the conditions that favor one favor the other.
Synthetic shoes (plastic, rubber, non-breathable synthetics) trap heat and moisture, creating the perfect bacterial incubator. Feet have over 250,000 sweat glands — more per square inch than anywhere else on the body. In a poorly ventilated shoe, all that moisture has nowhere to go, creating conditions where Brevibacterium and other odor-producing bacteria multiply rapidly. The smell is worse in summer and with prolonged wear.
How to Fix It
Target Brevibacterium Directly
$5-20This is the most effective approach — kill the bacteria causing the smell.
- 1Wash feet with benzoyl peroxide body wash (5-10%) or chlorhexidine soap daily — these specifically eliminate Brevibacterium.
- 2Pay attention to between the toes — this is where Brevibacterium concentrates most. Use a washcloth or soft brush to clean between all toes.
- 3Apply a thin layer of antibacterial foot powder (zinc oxide or boric acid-based) after drying — creates an inhospitable environment for bacteria.
- 4Zinc sulfate soaks: dissolve 1 tablespoon zinc sulfate in a basin of warm water and soak feet for 10-15 minutes 2x per week. Zinc has strong antibacterial properties and is commonly used for foot odor.
- 5Glycolic acid (10-15%) applied to clean dry feet reduces the dead skin cell substrate bacteria feed on.
Fix the Footwear Environment
$0-50Remove the conditions that allow Brevibacterium to thrive.
- 1Switch to leather, canvas, or mesh shoes that breathe — synthetic materials trap moisture that bacteria need.
- 2Rotate shoes daily — allow at least 24 hours between wearing the same pair so they fully dry out.
- 3Use cedar shoe inserts or cedar shoe trees — cedar absorbs moisture and has natural antibacterial properties.
- 4Machine wash insoles and replace them every 3-6 months — they accumulate bacteria that recontaminate freshly washed feet.
- 5Wear moisture-wicking socks (merino wool or copper-infused synthetics) rather than cotton or synthetic socks.
Treat Athlete's Foot if Present
$8-20Fungal infection amplifies bacterial odor and needs separate treatment.
- 1Use an OTC antifungal (clotrimazole, miconazole, or terbinafine) applied between toes and on soles daily for 2-4 weeks.
- 2Continue for 1-2 weeks after symptoms resolve — athlete's foot recurs if treatment stops too early.
- 3Keep feet dry — dry between toes thoroughly after showering, this is the single biggest factor in athlete's foot prevention.
- 4If OTC treatments fail after 4 weeks, see a doctor — prescription terbinafine or itraconazole may be needed.
- 5Disinfect shower floors and bathmats to avoid reinfection.
When to Call a Professional
Cheesy smell with severe skin breakdown, open sores, or spreading redness — possible secondary bacterial infection (cellulitis) requiring antibiotics.
Foot odor with diabetes — any foot skin changes or infections need prompt medical attention due to impaired healing and circulation.
Smell combined with thick, yellow, or deformed toenails — indicates fungal nail infection (onychomycosis) that won't respond to topical treatments and needs oral antifungals.
Foot odor unresponsive to any intervention after 6-8 weeks — see a dermatologist or podiatrist for culture testing.
How to Prevent It
Wash feet specifically — don't rely on soap running down from your body in the shower; actively wash between every toe daily.
Dry feet completely after washing, especially between toes — moisture is the primary enabler of both bacterial and fungal growth.
Rotate footwear and allow 24+ hours to dry between wears.
Wear moisture-wicking socks — merino wool is particularly effective at reducing foot moisture.
Apply foot powder (cornstarch, boric acid, or zinc oxide) before putting on socks to absorb excess moisture.
Go barefoot or wear open sandals when possible — removes the enclosed moist environment bacteria need.
The Cheese-Foot Connection: Real Science
The connection between smelly feet and smelly cheese isn't a coincidence or an analogy — it's the same bacterium, the same enzyme, and the same chemical compound. Brevibacterium linens is used commercially to produce the distinctive rinds and aromas of limburger, munster, Taleggio, Époisses, and many other washed-rind cheeses. The bacterium produces an enzyme called methionine gamma-lyase that converts the amino acid methionine into methanethiol, a volatile sulfur compound with a sharp, cheesy smell.
Cheesemakers actually cultivate Brevibacterium on cheese rinds by 'washing' the cheese with brine, wine, or beer — this creates the moist, slightly salty environment the bacterium needs, exactly analogous to the conditions inside a shoe. The fact that your feet smell like parmesan isn't just because both are smelly — it's because both are literally running the same biological process.
This also explains why the cheesy smell is so distinct from other foot odor types: vinegar-smelling feet are usually Staphylococcus producing acetic acid, while cheesy-smelling feet are dominated by Brevibacterium producing methanethiol. Knowing which bacterium you're dealing with tells you exactly what treatment to use.
Frequently Asked Questions
Parmesan contains significant concentrations of isovaleric acid and methanethiol — the same compounds produced by Staphylococcus epidermidis and Brevibacterium linens on feet. Parmesan's aging process concentrates these compounds, making it an easy reference point. If your feet smell more like sharp parmesan, Brevibacterium is dominant. If they smell more like sweaty gym socks, S. epidermidis isovaleric acid is more prominent.
Yes — genetics plays a role through sweat composition, skin microbiome composition, and foot anatomy. People with denser concentrations of apocrine glands on their feet, more methionine in their sweat, or skin microbiomes naturally dominated by Brevibacterium will have more cheesy odor. But environmental factors (shoes, hygiene, diet) have a bigger impact than genetics for most people.
Somewhat. Foods rich in methionine (the amino acid Brevibacterium converts to methanethiol) can theoretically increase the substrate for odor production. Methionine is highest in meat, eggs, fish, and dairy. However, the effect is much smaller than changing footwear and hygiene habits. Diet is a secondary factor.
Brevibacterium is deeply embedded in the skin surface and between toes. Normal soap reduces bacteria temporarily but they repopulate within hours. For persistent cheesy smell, you need antibacterial soap (benzoyl peroxide or chlorhexidine) used consistently, combined with addressing the shoe environment that keeps reintroducing the bacteria. The shoes themselves often smell worse than the feet — they need treatment too.