The baking soda, scientifically known as "sodium bicarbonate", "monosodium carbonate" or even "sodium hydrogen carbonate" is a white powder with the raw chemical formula NaHCO3. It is an anhydrous mineral with a basic pH (8) that results from the combination of salt and limestone. Despite its name, which can lead to confusion, baking soda has nothing to do with caustic soda or soda crystals.
This powder is versatile; it is used in cooking, cleaning, and beauty care. The quality demanded in cosmetics is inevitably much stricter than that required for its use in cleaning products. The granulometry and purity of the ingredient are thus strictly controlled in cosmetics.
In deodorant formulas, baking soda is particularly valued and acclaimed for its absorbent properties
However, it is important to clarify that very few scientific studies specifically support its use as a deodorant. Thus, only one study suggests that baking soda may have antimicrobial effects, which could mean it has the ability to combat the bacteria responsible for underarm odours. Nevertheless, it is important to note that this study is old and was conducted in the context of dentistry, not skincare.
It is thus established that baking soda absorbs the moisture present in the armpits, but its effect on odours is yet to be scientifically demonstrated.
Furthermore, it is better to use a deodorant containing baking soda rather than applying this pure ingredient directly under the armpits. Indeed, pure baking soda has a drying effect due to its alkaline pH, which is significantly higher than the physiological pH of the skin, which is acidic (around 5-6). In deodorant formulas, manufacturers generally lower the pH of the product for better skin compatibility, even if the deodorant still contains baking soda. Therefore, favour a baking soda deodorant over pure baking soda to combat underarm perspiration, especially if you have sensitive skin.