Why Do My Feet Smell Like Sour Milk?

Having feet that smell like sour milk can be an embarrassing and frustrating issue. But what actually causes this unpleasant foot odor? There are a few potential culprits.


One of the most common reasons for smelly feet is excessive sweating. There are more sweat glands in our feet than anywhere else in the body. When we sweat, bacteria on our skin break down the sweat and produce isovaleric acid, which gives off a cheesy, sour milk-like smell. People who sweat more tend to be more prone to having smelly feet. Wearing socks and shoes creates a warm, moist environment where bacteria can thrive.

Fungal Infections

A fungal infection on the feet, such as athlete’s foot, can also cause feet to smell like sour milk. The fungus itself as well as the excess skin cells it feeds on both contribute to the odor. Fungal infections alter the pH balance of the skin, making the feet produce more sweat, which encourages bacterial growth. The fungal infection causes the skin to become inflamed and peel or flake. The shedding skin cells fuel the foot odor.

Bacterial Overgrowth

Even without a fungal infection, having an overabundance of bacteria on the feet can lead to sour milk foot odor. Our feet naturally have lots of microbes living on them. But if the bacterial colonies grow too large, the byproducts the bacteria produce when breaking down sweat cause a foot odor. Wearing the same shoes every day can cause bacteria to overload if the shoes aren’t cleaned regularly.

Not Washing Feet Properly

Many people don’t take the time to properly wash their feet in the shower. Simply letting soapy water run over the feet is not enough. You need to vigorously scrub your entire foot including between the toes where sweat and dead skin cells can gather. Make sure to dry your feet thoroughly after washing as well, especially between the toes. Left damp, these spaces foster bacterial growth.

Sock and Shoe Materials

The materials that make up your socks and shoes also influence foot odor. Synthetic fabrics like polyester don’t allow ventilation or absorption of sweat like natural materials such as cotton and wool. Bacteria multiply rapidly in damp environments created by non-breathable shoes and socks. Choosing all cotton socks and leather or mesh shoes can help reduce excess moisture.

Medical Conditions

In rare cases, persistent severe foot odor can be a sign of an underlying medical condition. Overactive sweat glands, diabetes, athlete’s foot, and foot infections can all cause increased or foul foot odor. Issues like diabetes and circulatory disorders can keep feet from healing properly and cause bacterial buildup. See your doctor if improving hygiene doesn’t resolve very smelly feet.

The bacteria, fungus, and sweat on our feet interact to give foot odor its characteristic cheese-like smell. Focus on keeping feet clean and dry and wearing breathable materials to help combat sour milk smelling feet. But if measures like washing regularly and changing socks daily don’t help within a couple weeks, check with your doctor to rule out any underlying conditions contributing to the odor.