Sodium Bicarbonate in Skincare: Why NAYA Avoids It
- Sodium bicarbonate (baking soda) has a pH of approximately 9.5. Your skin's natural surface pH is approximately 5.5. That four-point gap is the problem.
- Applying sodium bicarbonate disrupts the acid mantle, destabilises the skin microbiome, increases barrier permeability, and elevates inflammatory load.
- In deodorants it is effective at neutralising odour - but causes contact dermatitis, burning and rash in a significant proportion of users, especially after shaving.
- Natural origin does not make a highly alkaline ingredient safe for skin. pH incompatibility is a chemistry problem, not a sourcing problem.
- NAYA's Botanical Deodorant Cream contains no sodium bicarbonate. It uses a prebiotic microbiome-active approach to odour neutralisation that works with skin biology rather than against it.
At NAYA, sodium bicarbonate appears on our No-No List. Our Botanical Deodorant Cream is formulated without it. The reason is straightforward: sodium bicarbonate is chemically incompatible with the skin's normal biology. Not because of its origin, but because of its pH.
What sodium bicarbonate is and why it ends up in skincare
Sodium bicarbonate (INCI: Sodium Bicarbonate) is a naturally occurring alkaline salt. In its most familiar form it is baking soda - the white powder in the back of the kitchen cupboard. It neutralises acids through a chemical reaction, which is what makes it effective at deodorising: odour-causing compounds under the arms are typically acidic, and sodium bicarbonate neutralises them efficiently.
For formulators of natural deodorants, this made it compelling. It is inexpensive, effective, has a short ingredient name that non-chemist consumers recognise as kitchen-safe, and avoids the controversy of aluminium salts found in conventional antiperspirants. Through the 2010s and early 2020s it became the default active in the natural deodorant category.
The issue is that while sodium bicarbonate neutralises acids well in a pipe or a bowl, the underarm skin is not a pipe. It is a living biological system with a tightly regulated surface chemistry that does not benefit from alkalisation.
The pH problem - by the numbers
The skin's surface pH of 4.5 to 5.5 is not arbitrary. It is actively maintained by the body through sebum secretion, sweat composition, and the metabolic activity of the skin microbiome itself. This slightly acidic environment is the foundation on which most of the skin's protective functions depend.
Sodium bicarbonate at pH 9.5 sits at roughly the same alkalinity as standard bar soap - a pH level that dermatologists routinely advise avoiding for facial cleansing precisely because it disrupts the acid mantle. Applying it under the arms - where skin is thin, frequently abraded by shaving, and in close contact throughout the day - creates the same disruption in a more vulnerable location.
The gap between pH 5.5 and pH 9.5 is not subtle. Each unit on the pH scale represents a tenfold difference in acidity or alkalinity. Sodium bicarbonate is ten thousand times more alkaline than the skin's natural surface environment.
What happens to the acid mantle
The acid mantle is the thin film of slightly acidic secretions that covers the skin surface. It is formed from a combination of sebum, sweat, and the metabolic byproducts of the skin microbiome. Its primary functions are to act as a chemical barrier against pathogens and environmental insults, to regulate the activity of skin enzymes involved in barrier maintenance, and to support the microbial balance on the skin surface.
When sodium bicarbonate is applied to skin, the neutralisation reaction it undergoes with the acid mantle effectively dissolves it. The surface pH rises toward alkaline. Enzyme activity in the stratum corneum - particularly the serine proteases involved in skin cell shedding and barrier formation - becomes dysregulated. Barrier lipid processing is disrupted. The skin surface becomes transiently more permeable.
The acid mantle is not just a pH reading. It is an active biological structure that the skin continuously works to maintain. Alkaline disruption does not wash off harmlessly - it triggers a cascade of compensatory responses that can take hours to days to resolve, and with repeated application, may not fully resolve between uses.
The microbiome disruption
The skin microbiome - the community of bacteria, fungi and other microorganisms that inhabit the skin surface - is not a passive passenger. It is a functional component of the skin's immune defence. The microbiome under the arms is particularly active: it includes bacteria that compete with odour-causing species, produce antimicrobial compounds, and help calibrate inflammatory responses.
This microbial community operates optimally at the skin's natural slightly acidic pH. The beneficial bacteria that dominate healthy underarm skin - Staphylococcus epidermidis and certain Corynebacterium species - prefer an acidic environment. Sodium bicarbonate at pH 9.5 creates conditions that are inhospitable to these organisms while being permissive to bacteria that thrive in alkaline conditions, including some that are more directly associated with odour production and opportunistic infection.
- Increased underarm odour over time despite continued deodorant use
- Itching, redness or rash - classic signs of contact dermatitis
- Burning sensation, particularly after shaving when barrier is abraded
- Persistent sensitivity that worsens with continued use rather than resolving
- Darkening of the underarm skin with prolonged use in some individuals
The irony of the mechanism is notable: sodium bicarbonate deodorants work initially by neutralising acid odour compounds, but the alkaline disruption of the microbiome can over time shift the microbial balance toward more odour-producing species - meaning the product progressively undermines the very outcome it is being used for.
Barrier permeability, abrasiveness and inflammation
Beyond the pH and microbiome effects, sodium bicarbonate is physically abrasive. The crystals are hard-edged particles that can create micro-abrasions on the skin surface, particularly in the thin, folded skin of the underarm area. These micro-abrasions increase trans-epidermal water loss and create entry points for irritants - including the sodium bicarbonate itself and any other allergens or potential sensitisers in the formulation.
The combination of alkaline pH disruption and physical abrasion explains why sodium bicarbonate deodorant reactions are particularly common after shaving. Shaving already temporarily compromises the barrier surface. Applying an abrasive alkaline compound to freshly shaved, barrier-disrupted skin is compounding two stressors simultaneously - which is why the reaction in this scenario often progresses quickly from mild redness to visible dermatitis.
Why natural origin does not resolve the pH problem
The argument for sodium bicarbonate in natural skincare rests heavily on its natural origin and kitchen-cabinet familiarity. Neither of these properties addresses its chemistry.
pH is not a sourcing attribute. A compound derived from a natural mineral deposit and a compound synthesised in a laboratory can have identical pH values and produce identical effects on skin biology. Sodium bicarbonate's pH of 9.5 is what it is regardless of where it was mined or how it was processed. The acid mantle responds to pH, not to provenance.
This is a version of the same reasoning that applies to other natural irritants - fragrance compounds from rose water, drying alcohols from fermentation, oxidised plant oils. The relevant question for any ingredient applied to skin is not where it came from. It is what it does to skin biology.
What NAYA uses instead
Effective odour control does not require alkalising the underarm skin. The underlying mechanism of odour production is microbial: skin bacteria metabolise fatty acids and proteins in apocrine secretions to produce volatile odorous compounds. The relevant intervention point is microbial metabolism, not the pH of the skin surface.
Prebiotic microbiome modulation
NAYA's Botanical Deodorant Cream uses a plant-based active that modifies the metabolic pathway of odour-causing bacteria - shifting their metabolism from lipids (which produce odorous compounds) to polysaccharides (which do not). This addresses odour at source without creating an alkaline environment or disrupting the microbiome's overall balance. The underarm skin's pH is preserved. Beneficial bacteria are not affected. The approach works with skin biology rather than overriding it.
What this means in practice
The Botanical Deodorant Cream provides 24-hour protection and has been tested on sensitive skin - including epicutaneous testing per ICDRG (International Contact Dermatitis Research Group) guidelines, with no skin reactions observed across 30 participants with sensitive skin over 72 hours. It is aluminium-free, sodium bicarbonate-free, fragrance-free, and housed in biodegradable packaging.
Frequently asked questions
Why is sodium bicarbonate bad for skin?
Sodium bicarbonate has a pH of approximately 9.5 - strongly alkaline. The skin's surface pH is approximately 5.5. Applying sodium bicarbonate disrupts the acid mantle, destabilises the skin microbiome, increases barrier permeability and elevates inflammatory load. This causes contact dermatitis, burning and rash in many users, particularly after shaving when the barrier is already compromised.
Is sodium bicarbonate safe in natural deodorants?
It neutralises odour effectively but disrupts underarm skin pH. Even at modest concentrations it is a common cause of contact dermatitis in natural deodorant users. The reaction is more frequent and more severe after shaving. NAYA's Botanical Deodorant Cream is formulated without sodium bicarbonate and uses a prebiotic microbiome-active approach instead.
What does sodium bicarbonate do to the skin microbiome?
The skin microbiome requires a slightly acidic pH of 4.5 to 5.5 to maintain protective balance. Sodium bicarbonate at pH 9.5 creates alkaline conditions in which beneficial bacteria struggle to survive. This disruption can paradoxically increase odour over time as the microbial balance shifts toward odour-producing species that tolerate alkaline environments.
Can baking soda be used on skin?
Baking soda can reduce odour temporarily and has uses in clinical wound cleansing. As a regular cosmetic ingredient on intact, healthy or sensitive skin, its highly alkaline pH makes it incompatible with normal skin biology. The acid mantle, microbiome and barrier function all depend on maintaining pH around 5.5 - the opposite of sodium bicarbonate's pH 9.5.
What should I use instead of sodium bicarbonate in deodorant?
Prebiotic and microbiome-modulating actives that modify the metabolism of odour-causing bacteria without altering skin pH. NAYA's Botanical Deodorant Cream uses a plant-based active that shifts bacterial metabolism from lipid-based pathways (odorous) to polysaccharide-based pathways (odour-neutral) - providing 24-hour protection without pH disruption or microbiome destabilisation.
Further Reading
- Ingredient Integrity in Skincare: Why Formulation Quality Matters More Than Trend Ingredients
- Damaged Skin Barrier: Why Sensitive Skin Keeps Getting More Reactive
- Phenoxyethanol: Why Sensitive Skin Should Avoid It
- Rose Water for Sensitive Skin: What the Evidence Shows
- The Rise of the Conscious Consumer: Why Skincare Transparency Matters
- The Science of Skin Resilience: The Biology Behind Barrier-First Skincare
© NAYA Skincare. All information is for educational purposes and does not constitute medical advice.
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