This website talks about natural deodorant with baking soda and ways to avoid darker underarms.
While there are many reasons that dark underarms may occur from deodorant, baking soda may cause some damage to the under arms leaving them to appear darker than before if the individual has sensitive skin.
Baking soda can raise the PH level in the skin for an individual causing them to become irritated, leading to thickening of the skin causing it to become darker.
There have been cases where individuals have had darker underarms in humid climates as opposed to dry climates as well.
Overall baking soda is a natural deodorant ingredient that seems to cause irritation to a lot of individuals and can lead to darker underarms, yet it varies.
https://www.beautsy.com/en/blogs/beautsy-blog/all-about-natural-deodorant-with-baking-soda/
Rating: Varies individual to individual