A bleach-like smell coming from your feet is almost always caused by ammonia in your sweat. Your body produces ammonia as a byproduct of breaking down protein, and when your liver can’t fully convert all of it into a less pungent waste product, the excess escapes through your sweat. Since your feet have more sweat glands per square centimeter than almost anywhere else on your body, they’re a prime spot for this sharp, chemical odor to concentrate.
The smell isn’t actually bleach (sodium hypochlorite), but ammonia has a strikingly similar sharp, chlorine-like scent that’s easy to confuse with it. Several factors determine how strong this odor gets, from what you eat to how well hydrated you are.
How Your Body Creates That Chemical Smell
Your body breaks down protein into amino acids for energy and tissue repair. A natural byproduct of that process is ammonia, a nitrogen-containing compound with a pungent odor. Normally, your liver converts most of this ammonia into urea, a much milder substance that leaves your body through urine. But when ammonia production outpaces the liver’s ability to process it, the surplus gets expelled through sweat instead.
Sweat ammonia concentrations in adults typically range from about 2.7 to 3.0 millimolar during exercise. That’s enough to produce a noticeable smell, especially in enclosed spaces like shoes where the sweat can’t evaporate quickly. When sweat pools and concentrates inside a warm shoe over several hours, that ammonia smell intensifies and takes on the sharp, chemical quality you’re noticing.
Diet Is the Most Common Trigger
The single biggest reason for ammonia-scented sweat is eating more protein than your body needs for immediate use, especially if you’re not eating enough carbohydrates alongside it. When carbohydrate stores run low, your body leans harder on protein as a fuel source, which generates more ammonia as a byproduct.
A study from the European Journal of Applied Physiology tested this directly. After just three days on a low-carbohydrate, high-protein diet (45% protein, less than 5% carbohydrates), participants had significantly higher ammonia concentrations in both their blood and sweat during moderate exercise compared to when they ate a balanced diet. The total ammonia lost through sweat was measurably greater on the low-carb diet. If you’ve recently started a keto diet, cut carbs, or increased your protein intake, that’s a likely explanation for the bleach-like foot odor.
Dehydration Concentrates the Odor
When you’re not drinking enough water, your body produces less sweat overall, but the sweat it does produce is more concentrated. The same amount of ammonia dissolved in less fluid means a stronger smell. Think of it like the difference between a few drops of bleach in a full bucket of water versus the same drops in a cup. Staying well hydrated dilutes ammonia in your sweat and helps your kidneys flush more of it out through urine before it ever reaches your sweat glands.
Exercise and Physical Activity
Intense or prolonged physical activity increases ammonia production in two ways. First, your muscles burn through glycogen (stored carbohydrates) faster, which pushes your body toward using protein for fuel. Second, the metabolic waste products from hard-working muscles include more nitrogen compounds that your body converts to ammonia. If you’re exercising regularly and noticing the smell mainly after workouts or at the end of active days, your body is simply producing more ammonia than usual during those periods.
The combination of exercise with a high-protein or low-carb diet amplifies the effect considerably. Eating a carbohydrate-containing snack before a workout can help reduce how much protein your body burns for energy, which in turn lowers ammonia output in your sweat.
When the Smell Could Signal Something Else
In most cases, bleach-smelling feet are harmless and diet-related. But a persistent ammonia odor that doesn’t respond to dietary changes can occasionally point to something worth paying attention to.
Kidney function plays a central role in filtering ammonia from your blood. When the kidneys aren’t working efficiently, more ammonia circulates through your system and exits through your skin. People with diabetes can develop ammonia-scented sweat when low insulin levels force the body to break down protein for energy, similar to what happens on a very low-carb diet. This is distinct from the more commonly discussed “fruity breath” of diabetic ketoacidosis, which is caused by ketones and smells more like nail polish remover. The ammonia smell specifically relates to protein breakdown and potential strain on kidney function.
Certain bacterial infections on the skin of the feet can also produce unusual odors. Erythrasma, a common bacterial skin infection that thrives in warm, moist skin folds, sometimes produces a noticeable odor alongside slightly scaly, reddish-brown patches. If you see discolored patches of skin between your toes or on the soles of your feet along with the smell, a bacterial cause is worth considering.
How to Reduce the Smell
Start with your diet. If you’re eating a high-protein or low-carb diet, adding more carbohydrates (even moderately) reduces how much protein your body burns for fuel and lowers ammonia production. You don’t need to overhaul your eating. Even shifting from 15% to 30% of calories from carbs can make a difference. Drink more water throughout the day to dilute ammonia in your sweat and help your kidneys process it more efficiently.
For your feet specifically, moisture control is key. Ammonia smell intensifies when sweat sits in an enclosed, warm environment for hours. Wearing moisture-wicking socks made from merino wool or synthetic athletic fabrics pulls sweat away from your skin. Changing your socks midday if you’re on your feet a lot makes a noticeable difference. Rotating between at least two pairs of shoes so each pair has 24 hours to dry out fully between wears prevents the buildup of ammonia residue.
Antiperspirants designed for feet can reduce sweat output directly. Aluminum-based antiperspirants work by temporarily forming a plug in the sweat duct that blocks flow, and they’re effective on feet just as they are under arms. Apply them to clean, dry feet at night before bed, which gives the active ingredient time to work while your sweat glands are least active. Over-the-counter foot sprays or roll-ons with aluminum chloride are widely available.
If the smell persists despite these changes, washing your feet with an antibacterial soap targets any odor-producing bacteria that might be amplifying the ammonia scent. Drying your feet thoroughly, especially between the toes, limits the warm, damp conditions where bacteria thrive.