Occasionally people ask about a rash after commencement of using our natural deodorant. There will be a period of adjustment when switching from antiperspirants to a natural deodorant. Some people will say that you are detoxing as the glands are opening up and allowed to sweat. Long term use of antiperspirants changes the types and number of bacteria that live in the armpit so it takes time for the body to re-adjust when using a natural deodorant as the microbiome in the armpit region changes.
Human sweat is slightly acidic with a pH range of 4 to 6. The pH of perspiration varies from person to person and is affected by age, gender, race, medication, diet, or even hormonal changes. The natural pH of an individual’s sweat can actually cause an irritation or even a burning sensation when mixed with baking soda.
Why? Baking soda is slightly alkaline with a pH range of 8 to 9. If your sweat is more on the acidic side, there may actually be a little chemical reaction between the alkaline baking soda and the acidic sweat. Think of the “volcanoes” you made in science class with alkaline baking soda and acidic vinegar. If your sweat is more acidic, this little volcano can cause an irritation called “Irritant Contact Dermatitis.”
Apply the deodorant sparingly and gently while your body is making these adjustments. If the rash persists for more than a few weeks discontinue use.
For a really thorough explanation read this article: