Why your natural deodorant doesn't stop smells and gives you a rash
So called "natural deodorants" have gone through a renaissance as of late as people have found more interest in being environmentally conscious. Generally, there is the view that being natural, means it is better or safer for you. While true in many instances, any deodorant can claim to be "natural" as there is no technical definition or regulation around using this word. That means a lot of nasty stuff can be included in other products, or also, some of them aren't even deodorants, just smelly concoctions. Natural deodorants can actually make you smell worse and can cause chemical burns.
Why natural deodorants typically don't stop body odor?
One problem with "natural" deodorants is that many of them are just random plant products put together: like coffee grounds, cocoa butter, aloe, teatree oil, and whatever else. These smell nice by themselves, but many of these compounds are perfect food for bacteria. And since bacteria cause body odor, you're essentially feeding the problem. Imagine how nice a chocolate cake smells when its freshly baked, but then leave it for a month in the rubbish bin and its going to smell really bad. These nasty odors come from the bacteria digesting all those good things in the cake. So don't be fooled by pleasant smells as they just feed the beast - the goal should be to not smell at all!
What ingredients should you look for in a natural deodorant?
Instead of feeding microbes, you want to kill them and prevent them from growing on your pits, on your masks, in your undies, or wherever else you might smell. Acids and bases are good at killing bacteria, so baking soda (a base) and various acids are potentially useful ingredients to stop microbes. However these chemicals can also cause chemical burns on skins if they are in too high of a concentration. Additionally, people can develop sensitivities to acids and bases, they can discolor clothing and skin, and also they can react with other chemicals to form new toxic compounds. So make sure to test out any deodorants, "natural" or otherwise.
Silver is another antimicrobial compound gaining popularity as it is antimicrobial and so it stops odors at their source, rather than masking them. SWIFF uses ionic silver, but most "natural" deodorants that contain silver use nano- or micro-particles of silver, which have significant downsides as they are not as good at stopping microbes and they contribute roughly 10,000x-10,000,000x more to environmental contamination than ionic silver. Silver nanoparticles are also a gross brown color.
The promise of ionic silver and the peril of nanoparticles and microparticles (this gets science heavy, skip if you don't feel up or it)
Silver nano- and micro-particles are essentially really tiny balls of silver, or in other words they are millions of silver atoms all bound together into a ball. They are in the same state as silver on your silver bracelet, called silver zero (Ag0).