Chemical reaction in homemade deodorant

Which ingredients in my homemade deodorant recipe are causing it to froth and overflow its container? Is there something I can add to stop this reaction?


Ingredients:


* Magnesium oil (made from magnesium chloride flakes and distilled water)
* Baking soda
* Witch hazel
* Aloe Vera gel
* Arrowroot powder
* Essential oils (lemon, orange blend and lavender)




The most likely culprit is something acidic reacting with the baking soda ([sodium bicarbonate](https://en.wikipedia.org/wiki/Sodium_bicarbonate)).


Try mixing separately:


* Baking soda and witch hazel
* Baking soda and aloe vera gel


My guess is that one of these two has an acidic buffer in it that's causing the baking soda to turn into a [science fair volcano](https://sciencebob.com/make-your-own-volcano/) on you. 


You could try adding some [calcium carbonate](https://en.wikipedia.org/wiki/Calcium_carbonate) to the mix (crush up an antacid tablet, or buy powder from somewhere). $\ce{CaCO3}$ is more basic than $\ce{NaHCO3}$, so it might neutralize enough of the acid that it avoids the foaming.


[Sodium carbonate](https://en.wikipedia.org/wiki/Sodium_carbonate), often sold as "washing soda", is essentially a more-basic version of baking soda and might also work. You have to be careful not to add too much $\ce{Na2CO3}$, though, because it could make the product too alkaline and thus irritating to the skin. In particular, *do not substitute washing soda for all of the baking soda*—only add the amount of washing soda needed to prevent the frothing.


There are harsher chemicals that you could use to neutralize the acidity, but I wouldn't recommend trying them in a household project like this.


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