Baking soda does work well for underarm odor, often surprisingly well. It neutralizes the fatty acids produced by bacteria on your skin, which are the actual source of body odor. But it comes with a real tradeoff: its high pH can irritate underarm skin, especially with daily use. Whether it’s “good” for your underarms depends on your skin’s tolerance and how you use it.
How Baking Soda Stops Body Odor
Sweat itself is mostly odorless. The smell comes from bacteria breaking down sweat into volatile fatty acids, like butyric acid. Baking soda is a base, and it reacts with these acidic compounds to form sodium salts that have no smell because they don’t evaporate into the air. It’s a straightforward acid-base reaction, and it works fast.
Baking soda also has genuine antibacterial and antifungal properties. Lab research shows that bicarbonate can drastically reduce bacterial counts, with one study finding a 1,000-fold reduction against common bacteria like E. coli and S. aureus at sufficient concentrations. So it’s doing double duty: killing some of the odor-causing bacteria while simultaneously neutralizing the smelly compounds they produce.
The Skin Irritation Problem
Healthy skin sits at a pH of about 5.5, which is mildly acidic. Your skin maintains this acidity on purpose. It supports the protective barrier of the outermost skin layer and keeps moisture in. Baking soda has a pH around 8 to 9, which is solidly alkaline, and applying it daily pushes your skin out of its comfort zone.
Research on repeated alkaline exposure shows the consequences clearly. In one study, skin treated with an alkaline product over a five-week period showed increased water loss through the skin’s surface, disrupted barrier function, and heightened sensitivity to further irritation. Essentially, alkaline products slowly weaken your skin’s protective layer, making it more vulnerable to anything else it encounters, including friction from clothing and the salt in your own sweat.
For some people, the reaction is immediate: a burning sensation, red or bumpy rash, localized swelling, or skin discoloration in the armpit area. These are signs of contact irritation, and they can show up within days of starting a baking soda deodorant. If you notice redness or itching after applying a baking soda product, stop using it and give your skin a few days without any deodorant to recover.
How to Use It More Safely
If you want to try baking soda on your underarms, diluting it is key. A common DIY recipe from Gundersen Health System uses equal parts baking soda and cornstarch (a quarter cup each) mixed into half a cup of coconut oil. The cornstarch absorbs moisture while the coconut oil creates a buffer between the baking soda and your skin. This brings the effective concentration of baking soda down to roughly 25% of the mixture rather than applying it straight.
Before committing to daily use, test a small amount on the inside of your forearm and leave it for 24 hours. If you see no redness, try a small amount on one underarm for a few days before going all in. People with sensitive skin, eczema, or anyone who shaves their underarms frequently should be especially cautious, since freshly shaved skin is more vulnerable to alkaline irritation.
You can also reduce the baking soda ratio further. Swapping some or all of the baking soda for arrowroot powder gives you moisture absorption without the pH issue, though you lose some odor-fighting power.
Alternatives That Are Gentler
Magnesium hydroxide has become a popular replacement for baking soda in natural deodorants. Rather than overwhelming bacteria with alkalinity, magnesium hydroxide binds directly to odor-causing bacteria to neutralize them. It’s a less aggressive mechanism that works for most skin types, including sensitive skin. It also leaves less visible residue than baking soda, which can leave white marks or a gritty feeling.
Other natural deodorant ingredients worth considering include zinc oxide, which has mild antibacterial properties, and activated charcoal, which absorbs odor compounds. None of these are antiperspirants, so they won’t reduce sweating. They only target smell.
Who Should Avoid It
If your underarm skin is already irritated, broken, or inflamed, baking soda will almost certainly make it worse. People who shave daily, have a history of contact dermatitis, or notice their skin reacts to fragranced products are at higher risk for baking soda burns. Darkening of the underarm skin is another reported side effect of prolonged use in people with sensitive skin.
Baking soda also won’t reduce sweating. If your concern is wetness rather than odor, it’s not solving your actual problem. It absorbs some moisture, but far less effectively than a traditional antiperspirant containing aluminum salts, which temporarily block sweat glands.
For most people, baking soda works as a short-term or occasional odor fix. As an everyday solution, its effectiveness comes at the cost of gradually compromising your skin’s natural barrier, and for a significant number of users, that tradeoff shows up as irritation within weeks.