What Happens After Baking Soda Works?

Baking soda has been used as a deodorant for generations.

The idea seems almost too simple: apply sodium bicarbonate under the arms, and odor disappears.

For many people, it appears to work.

Body odor is not produced by sweat alone. It develops when microorganisms living in the underarm transform components of our secretions into volatile compounds that we perceive as odor. Corynebacteria are important contributors, although they are not the only microorganisms involved. ^[1]

And those microorganisms do not live in isolation.

They are part of a microbial community that exists within a particular skin environment, shaped by moisture, sweat, sebum, temperature, nutrients and pH. Our skin naturally maintains a mildly acidic surface, and this environment helps influence which microorganisms are able to thrive. ^[2]

Baking soda introduces something very different.

Sodium bicarbonate is alkaline.

But being alkaline does not tell us exactly what happens when sodium bicarbonate is applied to human underarm skin. Sodium bicarbonate is a weak base, and the size and duration of any pH shift will depend on factors such as concentration, formulation, moisture and the buffering capacity of the skin itself.

That is precisely one of the measurements missing from modern human studies of baking soda used as an underarm deodorant.

Being alkaline does not automatically make baking soda harmful. But if something has the potential to change the environment in which our skin and its microorganisms live every day, it is worth asking what that means beyond the immediate disappearance of odor.

Because the question is not only:

It is also:

Does Baking Soda Really Work for Body Odor?

There is a reason baking soda has survived for so long as a home remedy for body odor.

Historical observations describe sodium bicarbonate as an effective underarm deodorant, and experimental research shows that sodium bicarbonate can also exhibit antimicrobial activity under certain conditions. ^{[3] [4]}

But the mechanism is not as settled as the popularity of the remedy might suggest.

One early explanation proposed that sodium bicarbonate could react with volatile fatty acids and convert them into less odorous sodium salts. Other possible mechanisms include changes in the local chemical environment and antimicrobial effects. ^{[3] [4]}

In other words, baking soda may influence odor through more than one pathway. Which of these mechanisms matters most when sodium bicarbonate is repeatedly applied to human underarm skin remains unclear.

Baking soda is so routinely recommended as a natural deodorant that it is easy to assume its effectiveness has been thoroughly investigated in modern human studies.

Modern human evidence specifically investigating sodium bicarbonate as an underarm deodorant is surprisingly limited. Much of what we know comes from older observations, experimental antimicrobial research and what we understand about the chemistry of sodium bicarbonate. ^{[3] [4]}

That is enough to suggest that baking soda can reduce underarm odor. But it is not enough to tell us how reliably it works, which mechanism matters most on human skin, or what repeated use means for the underarm environment over months or years.

Why Should We Protect the Underarm Microbiome?

The skin microbiome is part of the skin’s protective ecology. It is not simply something that happens to live on its surface.

The microorganisms living on our skin compete for space and nutrients, influence one another and produce metabolites that can change the conditions around them. They also interact with our skin barrier and local immune defenses. Together, these relationships can make it harder for potentially troublesome microorganisms to simply move in and take over. ^{[2] [5]}

This changes the way we might think about bacteria under our arms. Eliminating bacteria is not automatically the same as protecting the skin. When we disturb a microbial community, we may affect not only microorganisms involved in odor, but also the ecological relationships that help make our skin resilient.

And like every living community, the skin microbiome depends on its environment. Moisture, nutrients, temperature, sebum, sweat and pH all help determine which microorganisms thrive and which struggle to compete. ^[2]

Our skin naturally maintains a mildly acidic environment. Change that environment repeatedly, and we have reason to ask whether we are also changing the community it supports.

Sodium bicarbonate is alkaline. So while it may reduce odor, repeated use also raises a different question: what happens when we repeatedly alter one of the environmental conditions that helps shape the microbial community our skin lives with?

Can Baking Soda Affect the Skin Barrier and Underarm Microbiome?

The relationship also works both ways.

The resident microbial community can contribute to processes that support an intact skin barrier, while the barrier itself helps create the environment in which that community lives. Disturb one, and the other may be affected too. ^{[2] [5]}

This matters because the skin barrier is our physical and chemical shield against the outside world. It helps keep water in while limiting the entry of irritants, allergens and potentially harmful microorganisms. When that shield becomes compromised, the skin becomes more vulnerable to its environment. ^[5]

Irritation can be one visible sign that the skin is not tolerating an exposure well. The underarm may be particularly vulnerable after shaving, waxing or other forms of hair removal, when friction and small disruptions of the skin barrier can temporarily increase sensitivity. Burning, redness, itching, dryness or increased sensitivity are therefore more than cosmetic inconveniences. They can be signals that the skin is not tolerating what is being applied to it.

This gives us another reason to look beyond whether baking soda eliminates odor. If repeated alkalization changes the microbial habitat, we also need to ask what that could mean for the barrier that this habitat interacts with.

But biological plausibility is not evidence that baking soda damages the skin barrier or microbiome, and a higher pH is not automatically harmful.

^{[3] [4]}

What Happens After It Works?

Suppose baking soda eliminates odor.

We apply it, the odor disappears, and eventually we stop using it. What happens next?

The skin does not remain permanently alkaline after every alkaline exposure. Human skin has mechanisms that help move surface pH back toward its baseline acidic state. How quickly that happens depends on the exposure, formulation and conditions involved. ^[6]

But pH is only one part of the picture.

How Long Does Skin pH Take to Recover After Using Baking Soda?

Studies of other alkaline exposures show that skin pH can move back toward its acidic baseline after the exposure ends. ^[6] But that does not establish how quickly underarm pH recovers after baking soda specifically, particularly after repeated daily use.

And even knowing when pH returns to baseline would answer only part of the question.

Skin pH may recover on one timeline. Barrier physiology may follow another. And a microbial community that has been disturbed may reorganize on yet another.

Human experimental research outside the underarm illustrates why these processes should not simply be assumed to happen simultaneously. In one acute skin-stress model, microbiome parameters normalized over a period of approximately two to seven days, while skin physiology and surface pH were measured alongside them. ^[7] This was a forearm model involving tape stripping and leave-on lotions, not baking soda used as a deodorant, so it cannot tell us how the underarm responds to sodium bicarbonate.

But it gives us a useful biological question.

Think of pH as one of the environmental conditions that helps determine which microorganisms can live comfortably on our skin. If that environment changes for long enough, some microorganisms may tolerate the change better than others. When the original acidic conditions return, the pH may look normal again, but the microbial community that forms part of our skin’s protective shield may not yet be the same.

These microorganisms do more than occupy our skin. They compete for space and nutrients, produce metabolites and interact with the skin barrier and local immune defenses. Together, they are part of the protective ecology that helps make our skin resilient.

How this recovery unfolds after repeated baking soda use under the arms has not been established.

In fact:

That missing experiment is central to this entire question.

Is a Higher Skin pH Always Harmful?

No.

pH does not act in isolation.

One short-term human study illustrates why. Zinc oxide reduced total recoverable bacterial growth, including odor-associated Corynebacteria and Staphylococcus hominis, and reduced perceived malodor even though axillary pH increased by approximately 0.5 units. ^[8]

But this relatively modest increase should not be equated with applying baking soda directly to the underarm. Sodium bicarbonate itself is alkaline, and depending on its concentration, formulation and how it is used, it may create a substantially different alkaline exposure. How large that pH shift actually is on human underarm skin has not been adequately established in modern studies.

In this particular intervention, malodor and odor-associated bacteria decreased even though axillary pH increased. ^[8]

It does not show that raising skin pH is harmless, nor can its findings be transferred directly to baking soda. Instead, it illustrates that the biological effect of an underarm product cannot be predicted from the direction of its pH change alone.

In this case, the authors attributed the anti-odor effect primarily to zinc oxide’s antibacterial activity. ^[8]

The study also lasted only 13 days. It did not establish what maintaining a higher axillary pH would mean for barrier function or the broader microbial community over months or years. ^[8]

Thirteen days also tells us little about cumulative irritation. A product that appears tolerable over days may behave differently when it is applied repeatedly for weeks or months, particularly to skin that is frequently shaved, exposed to friction or already irritated.

Nor does the study tell us what happens when the skin is repeatedly exposed to a directly alkaline substance such as baking soda, particularly if the resulting pH shift is larger or persists for longer.

So the question is not whether pH must never change.

And for baking soda, that leaves us with a remarkably basic question that modern research has not yet answered:

Can Baking Soda Eventually Make Body Odor Worse?

There is currently no strong evidence that regular baking soda use causes “rebound odor” or permanently makes body odor worse.

Deodorant and antiperspirant studies show that repeated product use can alter axillary microbial communities, but these findings cannot be transferred directly to baking soda. ^{[9] [10]}

Whether repeated sodium bicarbonate use could change the underarm environment in ways that temporarily influence odor after stopping has not been established.

What Should Our Long-Term Goal Be?

That means supporting the conditions our underarm skin naturally tries to maintain: a mildly acidic pH, an intact skin barrier and a microbial community that forms part of its protective ecology.

These elements do not exist independently. The skin barrier helps create the habitat in which microorganisms live. The microbial community interacts with that barrier and with local immune defenses. And pH helps shape which microorganisms are able to thrive and compete within this environment. ^{[2] [5]}

When these relationships are working well, we may not need to wage war on every bacterium involved in body odor. Instead, we can ask whether the environment itself can make it more difficult for odor-producing microorganisms and their metabolic activities to dominate.

And that changes the question we ask of a deodorant. Not only:

But also:

Can We Control Odor by Supporting the Skin Environment?

Sodium bicarbonate can show antimicrobial activity under experimental conditions. ^[4] But controlling body odor does not necessarily require broadly suppressing the microbial community.

Odor can potentially be approached in different ways: by supporting a mildly acidic skin environment, including through formulations whose pH is adjusted with ingredients such as lactic acid, reducing excessive odor-producing microbial activity, binding or neutralizing odor molecules, or using more targeted antimicrobial strategies when needed.

Zinc ricinoleate, for example, has been studied as an odor absorber rather than primarily as a way to eliminate bacteria, while zinc oxide has reduced odor-associated bacteria and perceived malodor in short-term human research. ^{[8] [16]}

Zinc ricinoleate reduced the perception of existing axillary malodor in controlled deodorancy research, illustrating that odor can be addressed without making bacterial elimination the central mechanism. ^[16]

Perhaps not.

For something used every day, it may be reasonable to consider formulations that are compatible with the skin’s naturally mildly acidic environment rather than focusing only on eliminating bacteria.

Human research also shows that deodorant formulations can shift axillary pH toward a more acidic range. In one open study involving 48 participants, the tested formulations reduced mean axillary pH during use, with values returning toward baseline during washout. ^[17] This does not establish that lowering pH alone is sufficient to control odor, nor does it demonstrate that every acidic formulation will behave in the same way.

Plant-derived compounds offer one interesting avenue to investigate. Sage, hops and other botanical extracts have demonstrated activity against microorganisms associated with axillary odor, and some botanical formulations have reduced malodor in short-term human studies. ^{[11] [12]}

But “plant-derived” does not automatically mean gentle, selective or microbiome-friendly. Each ingredient and formulation needs to be evaluated on its own.

So What Can We Actually Do About Body Odor?

The first step may be to stop thinking about body odor as a single-cause problem.

Underarm odor emerges from an interaction between secretions produced by our body, the microorganisms that transform them and the compounds created through that metabolism. ^{[1] [14]}

And that means the way we smell can vary.

What Causes Body Odor to Change?

Diet, health, climate, hygiene and other individual factors may influence the way we smell. Hormonal changes may also be worth considering when body odor changes, although they should not automatically be assumed to be the cause. ^[14]

Some human research suggests that dietary patterns can influence perceived body odor, although the evidence remains limited and does not justify a simple “body-odor diet.” ^[13]

When body odor changes, it can be useful to look for patterns: whether the change appeared after particular foods, with heavier sweating, around hormonal changes, after starting a medication, or in connection with certain fabrics or clothing routines.

These observations cannot diagnose the cause, but they may help reveal patterns.

Hygiene matters too, but keeping the underarm clean does not require trying to sterilize it. And persistent irritation should not be accepted as the necessary price of odor control.

Burning, redness, itching, dryness or recurrent sensitivity are reasons to reconsider what is being applied to the skin.

The same caution applies when an existing skin condition affects the underarm. In that situation, experimenting with home remedies or strongly altering the skin environment without medical guidance may not be appropriate. Baking soda is no exception.

Sometimes the better question is not:

but:

When Should a Change in Body Odor Be Checked?

Most variation in body odor is not evidence of disease.

But persistent, unexplained or distinctly unusual changes deserve attention, particularly when they occur alongside other symptoms.

Certain metabolic, infectious and other medical conditions can alter compounds released by the body, although body odor alone cannot establish a diagnosis. ^[15]

If a change is persistent or concerning, it makes more sense to investigate the reason than simply to use progressively stronger products to cover it.

What Does the Evidence Tell Us About Baking Soda?

Baking soda may work remarkably well for body odor.

That is precisely why it deserves a more interesting scientific question than simply whether it works.

Sodium bicarbonate is alkaline. It can influence odor chemistry and has demonstrated antimicrobial activity under experimental conditions. Historical human observations also support its deodorizing potential. ^{[3] [4]}

What remains uncertain is what repeated daily use means for the underarm as a living environment.

We do not have convincing long-term human research following regular baking soda use while simultaneously measuring skin pH, barrier function, microbial composition and what happens after the product is stopped. ^{[3] [4]}

That does not prove that baking soda damages the skin microbiome.

It also does not prove that long-term use is biologically neutral.

And perhaps that is the most useful conclusion.

When something works immediately, we naturally focus on the result we can see or smell. But skin health asks us to think further ahead.

The better question may not be how completely we can eliminate the microorganisms associated with odor.

It may be: