Baking soda: a very low-abrasion toothpaste cleaner that lifts stain and slightly reduces plaque and gum bleeding. In deodorants it neutralises odour but often irritates.
In toothpaste and mouthwash, baking soda is a soft abrasive (pure baking soda has an RDA of about 7, far below silica) that still removes surface stain well, and it buffers plaque acids. It tastes salty, which is why some pastes are mostly baking soda and others use a little.
In deodorants it neutralises the acidic compounds that smell. It is alkaline, and a common reason 'natural' deodorants cause red, itchy or darkened underarms.
A 2019 systematic review found baking soda pastes remove more plaque in single-brushing tests, only partly confirmed in longer trials, and slightly reduce gum bleeding. A network meta-analysis ranked it among the weaker toothpaste additives for gingivitis. Stain-removal evidence is good but comes from narrative reviews. The deodorant irritation point is from clinical experience, not trials.
21 publications: baking soda paste removed more plaque in single-brushing studies, only partly confirmed in longer studies; gum bleeding fell slightly versus control pastes, with no difference in gingival index. Moderate risk of bias, high heterogeneity.
In lab and clinical studies, baking soda toothpastes removed extrinsic stain effectively and safely despite relatively low abrasivity, in several studies better than more abrasive non-baking-soda pastes.
53 six-month trials. Among rinses, essential oils, chlorhexidine (0.10% or more) and cetylpyridinium chloride (above 0.05%) had the largest effects on gingivitis, with essential oils ranking highest; active toothpastes differed little from each other, with baking soda among the weakest.