Welcome to the fourth in this mini series about deodorants and what makes them tick. I have had some great input and a couple of questions from you guys that put me on an information excursion about a popular ingredient in many DIY deodorants: sodium bicarbonate (also known as bicarbonate of soda or baking soda).

Baking soda deodorant is a fairly simple melt and mix recipe that can be found on many forums and blogs about DIY beauty. The recipe – in broad strokes – baking soda is mixed with coconut oil and/or shea butter, cornstarch and/or arrowroot and optional essential oils. Proportions vary slightly, but the basic idea is the same.

Baking Soda is Good For a Slew of Things
Sodium bicarbonate is a pretty versatile ingredient. Because it is amphoteric (reacts with both acids and bases), it has numerous uses. It is at hand in almost every laboratory and found in almost every kitchen. Taken internally, it functions as an antiacid.  Mixed with water and applied as a paste, it helps reduce itchiness from insect bites or poison ivy. This same paste functions as an effective cleaning and scrubbing agent for kitchen and bathroom surfaces. Bicarbonate soda helps control fungus growth and is a known absorbant of musty smells (as many a used-book salesperson will happily tell you). It’s understandable that this multifunctional ingredient would be an obvious choice as the active in a homemade deodorant. It is quite an effective deodorizer.

So What’s the Problem?
The problem is that baking soda causes some level of increased sensitivity in the skin of most users after a short period of time. I’ve read numerous accounts of ‘burning sensation’, rash, flaking and even ‘skin going leathery’. Sodium bicarbonate’s MSDS (Material Safety Data Sheet) does indeed warn that ‘continuous contact may cause skin irritation (red, dry, cracked skin).’ (See one MSDS example here.)

Mind you, not everyone gets these skin reactions. I’ve also seen accounts of people that were thrilled with how well their baking soda deodorant worked and had no complaints. But in all fairness, these folks belong to a minority.

Skin reactions or not – no one seems happy about applying baking soda deodorant directly after shaving.

I think I know why.

A Question of Balance 
Among its many uses, sodium bicarbionate is used for effectively raising the pH balance of water.

Baking soda has an average pH of 8.3.

If you check the label of any skin care product that advertises being ‘tolerated by even the most sensitive skins’, you will find a pH between 5.0 and 5.5. If you check the pH of many deodorants, you will often find it lies somewhere between 4.5 and 5.0.

Aloe Vera – which is so skin friendly it is even recommended for toddlers – has a pH of approx 4.5.

Even though it is an effective deodorizer, sodium bicarbonate is unfortunately on the harsh side of skin friendly.

LisaLise Armpit Requirements
When I started developing my own deodorants, one of my main requirements (apart from the obvious deodorizing one) was that they could be applied directly after shaving with no irritation or sensitivity of any kind. I succeeded. For this reason alone, I do believe I am quite happy to abstain from giving baking soda deodorant a try.

I must admit though, I have a certain admiration for the ladies and gents that are able to use baking soda deodorant without experiencing any sensitivity. What hardy stuff they must be made of!

UPDATE: A slew of comments and letters have prompted this post about skin reactions from DIY baking soda deodorant.