Natural deodorant gives you a rash mainly because of baking soda. Sodium bicarbonate sits at around pH 8 to 9, while your skin sits at around pH 5, and daily use of something alkaline on thin underarm skin damages the barrier. The result is redness, itching and sometimes darker skin. A bicarb-free formula avoids it.
It starts as a bit of itch. Then a patch of red you notice in the mirror after a shower. For some people the skin goes darker and stays that way for weeks after they stop.
Almost everyone draws the same conclusion: my skin is too sensitive for natural deodorant. Then they stop looking.
Here's the part that rarely gets explained. It is usually not your skin. It's the baking soda, and there's a straightforward reason why.
Your skin likes acid. Bicarb is alkaline.
Skin sits at about pH 5, and that slight acidity keeps the barrier working and the bacteria on your skin in balance.
Baking soda sits at about pH 8 to 9. It handles odour precisely because bacteria struggle in alkaline conditions. Your skin barrier struggles too.
Why the underarm is the hard part
Rub something alkaline into thin underarm skin every morning and the barrier takes a hit. For some people nothing happens. For plenty of others it's redness, itching, stinging in the shower, sometimes a darker patch that lingers.
Under the arm, everything is amplified. The skin is thinner than on your arms or face, it absorbs more readily, it stays warm and damp, and it gets shaved. Safe levels for a lot of ingredients are tighter there for exactly this reason.
Why it gets worse at some points in life
A brand that worked fine for years can turn on you. Hormonal change, pregnancy and the postpartum months often come with more sweating and skin that reacts to things it used to tolerate.
Nothing about that means your skin has become a problem to be managed. It means the product has less room for error than it did.
The sensitive tax
Once bicarb rashes became common knowledge, the fix most brands landed on was a second product: a sensitive version, off to one side, usually with fewer scents and sometimes a higher price.
That is a strange arrangement. The version that doesn't hurt is treated as the exception, and you pay extra to get out of a problem the formula created.
What we use instead
bodi is bicarb-free in the core formula. Not a sensitive line, not a variant. Every scent, from day one.
The main swap is magnesium hydroxide. It handles odour in a comparable way to baking soda without the jump in pH, so it isn't fighting your skin barrier while it works. Triethyl citrate and zinc ricinoleate take on the rest, spreading the job across three actives rather than one.
Then the formula tries to leave your skin better than it found it. Shea butter and fractionated coconut oil soften. Cetyl alcohol, a fatty alcohol rather than the drying kind, keeps moisture in. Tapioca starch handles the wet. It's paraben-free and aluminium-free too.
Really amazing! Husband usually is allergic but isn't to this one.
An honest account of the switch
Coming off an antiperspirant is a real adjustment, and we would rather tell you than have it surprise you.
An antiperspirant reduces how much sweat reaches the surface. Stop using it and your sweating returns to normal, which for a week or two can feel like more than normal. Your skin bacteria also settle into a new balance. Some people notice a stronger smell for a few days. Some notice nothing at all.
- Apply to clean, dry skin in the morning, rather than over yesterday's layer.
- Give it a fortnight before you judge it.
Whatever you've heard it called, it isn't a purge of anything. Your old deodorant wasn't poisoning you. It's a change, and it settles.
Common questions
How long does a bicarb rash take to settle?
Once you stop using the product, irritation usually calms over a few days. Darker patches can take longer to fade. If the skin is broken, weeping or not improving, see a pharmacist or your GP rather than experimenting with another deodorant.
Is baking soda in every natural deodorant?
No, but it's common, because it's cheap and it works on odour. Check the ingredient list for sodium bicarbonate. Several brands now sell a separate bicarb-free line alongside their original.
Does bicarb-free mean it works less well?
Not if the formula is built around other actives. bodi uses magnesium hydroxide, triethyl citrate and zinc ricinoleate together, so the odour control doesn't depend on a pH spike.
Can I use it after shaving?
Wait until the skin settles, ideally a few hours, and apply to clean, dry skin. Freshly shaved skin reacts more to anything you put on it.
It's worth one more try.
Check your current stick for sodium bicarbonate. If it's in there, you have your answer. Minis are three small ones, which is a low-stakes way to find out whether bicarb was the problem all along.
Read next
Start with the honest guide to natural deodorant in NZ. Then: why your natural deodorant quits at 3pm, and how refillable deodorant actually works.
