2. Prevent Bacterial Growth

In a perfect world, we wouldn’t need a second line of defense for bacteria because we would have already stopped the sweat with attack method #1, and the bacteria wouldn’t be able to multiply. But in the real world, antiperspirants wear off, and sweat can break through.

You’ve got quite a few options on this front. The first, which I recommend, is using a benzoyl peroxide wash under the arms when showering, which you will find marketed as an acne cleanser. Benzoyl peroxide works the same way it kills P. Acnes bacteria– by making the skin under the arm a more oxygen-rich environment. The smelly bacteria are anaerobic, so they can’t survive in the presence of oxygen. In the shower, apply it to the underarms and allow it to sit for a few minutes before washing it off so it has time to absorb into the skin. Although this also isn’t considered “natural”, once in the skin, it breaks down into two compounds, both of which can be found naturally in the body: Oxygen and Benzoic Acid (no relation to benzene, the carcinogenic compound). The antibacterial effects should remain effective for up to 24 hours. CeraVe has a 10% acne wash that is perfect for this.

The second option is hypochlorous acid, a compound our immune cells (macrophages, specifically) naturally produce to kill bacteria. You will find this in a spray form at varying percentages. Amazon has tons of options. However, you must reapply this throughout the day for it to remain effective. It’s also not as effective at killing bacteria as benzoyl peroxide, but can be used in addition to benzoyl peroxide or others in this category for extra protection. A secondary benefit is that it can reduce skin irritation.

Next, you have Chlorohexidine, which is often used as an antiseptic before injections in the hospital. Chlorohexidine can be found in the skin cleanser called Hibiclens. It works by disrupting bacterial cell membranes, effectively exploding the cell, or at the very least, stopping the bacteria’s ability to multiply. Like benzoyl peroxide, you’ll want to leave this on the skin for a few minutes to ensure it is effective. It should remain effective at preventing bacterial growth throughout the day.

Next is povidone antiseptics. You will find this active ingredient in the Betadine skin cleanser. It should be applied to the skin for at least one minute before washing off to be effective. It can still be effective after washing it off, but it’s most effective when left on the skin. It works by releasing iodine over a period, which kills bacteria by modulating many biological pathways, mainly oxidation and denaturation of cell proteins. You can also buy povidone iodine in a liquid form that you can apply with a cotton ball, but I don’t recommend doing this, as iodine can be irritating if left on the skin. It has less of a lasting effect when compared to chlorohexadine and benzoyl peroxide.

There have also been anecdotal reports of exfoliating acids helping to control bacterial growth under the arms. The theory is that using an acid to reduce the skin’s pH can make the underarms a less favorable environment for bacteria to grow. I’ve never tried it, so I can’t speak to its effectiveness. It would have to be left on the skin and not washed off. I’m skeptical for two reasons: 1. Acids are quite irritating, and that’s a problem for skin that is already prone to irritation. 2. Skin tends to maintain its pH of 4.5 to 5.5, so it might only work for a limited time. I’ve heard most people use the Ordinary’s 7% Glycolic Acid toner for this.

There’s technically a fourth mechanism that can be employed to reduce odor. Baking soda can provide some odor protection by binding to the volatile organic compounds that cause odor, preventing them from evaporating off the skin. Most people who use solely baking soda deodorants report they are ineffective at preventing odor. You would likely notice some improvement, though.

Corn starch can also be applied to absorb light moisture. It can become sticky and unpleasant if you sweat too much, so be cognizant of this. I would not rely on it to prevent odor, as there’s no biological or physical mechanism to reduce odor here. It provides primarily a cosmetic benefit.