Baking soda has real antimicrobial and exfoliating properties, but its high pH makes it a risky choice for routine skin care. Healthy skin maintains a slightly acidic surface (pH 4.5 to 5.5), while baking soda dissolved in water sits around pH 8 to 9. That gap is large enough to disrupt your skin’s protective acid mantle, potentially causing dryness, irritation, and increased vulnerability to infection. In certain limited uses, like diluted baths for psoriasis, there’s evidence it can help. For everyday facial or body care, the downsides generally outweigh the benefits.
Why pH Matters for Your Skin
Your skin’s outermost layer is coated in a thin, slightly acidic film called the acid mantle. This layer, which sits at an optimal pH around 5.0, does several important jobs: it holds in moisture, supports the community of beneficial bacteria living on your skin, and activates enzymes that repair and maintain the skin barrier. When something pushes that pH higher (more alkaline), these processes start to break down.
Baking soda in water creates a solution around pH 8 to 9, which is roughly 1,000 times more alkaline than healthy skin (pH is a logarithmic scale, so each whole number represents a tenfold change). Applying it directly raises the skin’s surface pH, increasing water loss through the skin and shifting the bacterial balance. Research has linked a more alkaline skin surface to inflammatory conditions including atopic dermatitis and acne, which is ironic given that many people reach for baking soda specifically to treat breakouts.
Baking Soda as an Exfoliant
Baking soda crystals range from about 90 to 250 microns in size, making them fine enough to act as a physical exfoliant. When mixed into a paste and rubbed across the skin, these crystals abrade dead skin cells from the surface. Patented formulations for facial peels use baking soda as the primary abrasive agent, sometimes mixed with aloe and cornstarch to create a gentler gel consistency.
The problem is control. Unlike commercial exfoliants with uniform, rounded particles, baking soda crystals have an irregular, angular shape. Pressing too hard or scrubbing too long can create micro-abrasions on the skin’s surface. These tiny tears compromise the barrier and can leave skin red, dry, or more prone to breakouts. If you do use baking soda as a scrub, keeping it to once a week, using a very light touch, and rinsing thoroughly reduces the risk. But gentler exfoliants with smoother, more uniform particles are a safer bet for most people.
Does It Actually Fight Acne?
Baking soda does have antimicrobial properties. Lab studies have shown it can inhibit certain fungi and bacteria, particularly Candida albicans (a yeast) and Streptococcus mutans (a bacterium responsible for tooth decay). Some researchers have explored its potential against Staphylococcus aureus, a pathogen behind several common skin infections including boils and folliculitis.
Here’s the catch: none of these antimicrobial studies have been conducted on living human skin. The leap from a petri dish to a complex, inhabited skin surface is significant. Your skin hosts an entire ecosystem of microorganisms, and the acid mantle helps keep beneficial species in check while suppressing harmful ones. Raising the pH with baking soda disrupts that balance indiscriminately, which could theoretically make acne worse over time by allowing problem-causing bacteria to flourish. No clinical trials support using baking soda as an acne treatment.
Baking Soda Baths for Psoriasis
One area where baking soda has actual clinical support is in diluted baths for mild to moderate psoriasis. In a study of 31 patients, those who bathed in sodium bicarbonate solutions over 21 days reported statistically significant improvements in itchiness and irritation compared to a placebo group. The improvement was meaningful enough that patients continued the baths on their own after the study ended.
The key difference here is concentration. A few tablespoons of baking soda dissolved in a full bathtub creates a much milder alkaline solution than a paste applied directly to the skin. The large volume of water dilutes the pH shift considerably, and the soak time is limited. Researchers have noted that even in an era of advanced biologic therapies for psoriasis, this older approach still has a role as a low-cost complementary option for symptom relief.
People with eczema sometimes try baking soda baths for similar reasons. While the anti-itch effect may provide temporary relief, eczema-prone skin already tends to have an impaired barrier and a higher-than-normal pH. Adding an alkaline soak could worsen barrier dysfunction in some individuals, so starting with a very small amount and monitoring your skin’s response is important.
Why It Irritates Underarms
Baking soda shows up in many natural deodorants because it neutralizes the acidic compounds that cause body odor and slows odor-producing bacteria. It works well for this purpose, which is why it keeps appearing in formulations despite a well-known downside: underarm rashes.
Armpit skin is thinner and more sensitive than skin on most of the body. It’s also frequently shaved or waxed, which removes the outermost protective layer and creates tiny nicks. Applying a product with a pH of 8 to 9 onto this compromised skin pushes it far outside its comfort zone. The result is often redness, burning, peeling, or a bumpy rash. People with sensitive skin are especially vulnerable, but even those with resilient skin can develop irritation after weeks or months of daily use.
If you like baking soda deodorants but notice irritation, switching to a formula that uses a lower concentration or buffers the pH with other ingredients can help. Skipping application on days you shave gives the skin time to recover its acidity.
Safer Alternatives for Common Uses
- For exfoliation: Chemical exfoliants like alpha-hydroxy acids work at a skin-friendly pH and dissolve dead cells without physical abrasion. They’re more predictable and less likely to cause micro-tears.
- For acne: Benzoyl peroxide and salicylic acid have extensive clinical evidence behind them. They target acne-causing bacteria and unclog pores without disrupting the acid mantle as aggressively.
- For itchy skin: Colloidal oatmeal baths are well-studied for itch relief and work at a near-neutral pH, making them gentler on the skin barrier.
- For odor control: Zinc-based or magnesium-based deodorants neutralize odor without the same pH disruption. Arrowroot powder and kaolin clay absorb moisture without raising alkalinity.
Baking soda isn’t dangerous in the way a toxic chemical would be. Occasional, diluted use is unlikely to cause lasting harm for most people. But as a daily skin care ingredient, it works against the very system your skin relies on to stay healthy. The acid mantle exists for a reason, and the most effective skin care routines respect it rather than override it.