At a Glance
- Boric acid and sodium borate are chemically related but not identical compounds
- Both are approved in the US at concentrations ≤5% but banned in EU cosmetics since 2019
- Sodium borate has a higher pH (9-11) making it more alkaline and potentially more irritating
- Boric acid shows lower skin absorption through intact skin but penetrates damaged skin readily
- Both compounds raise reproductive toxicity concerns based on animal studies
- Common products containing these ingredients include creams, lotions, shampoos, and bath products
- The cosmetics industry recommends avoiding both on infant skin and damaged/broken skin
- Neither compound should be used on abraded, burned, or wounded skin due to enhanced absorption
The personal care industry relies on numerous chemical compounds to preserve products, adjust pH levels, and maintain stability. Two related ingredients that frequently appear in cosmetic formulations are boric acid and sodium borate (borax). While chemically similar and often discussed together in safety assessments, these boron-containing compounds have distinct properties that affect their performance and safety profiles in skincare, haircare, and other personal care applications.
Sodium Borate and Boric Acid are used in cosmetics as preservatives, antiseptics, water softeners, pH adjusters, emulsifiers, neutralizes, stabilizers, buffers, or viscosifiers. Their versatility makes them attractive to formulators, yet growing regulatory scrutiny and consumer concerns have raised questions about whether these ingredients belong in products applied to skin and hair.
Understanding the differences between boric acid vs sodium borate helps both consumers and manufacturers make informed decisions about product safety and formulation choices.
Boric Acid vs Sodium Borate: Chemical Distinctions
While often lumped together in discussions, boric acid and sodium borate are distinct chemical entities with different structures and properties.
Borax is a naturally occurring mineral, also known as sodium borate, sodium tetra borate, or disodium tetra borate, and it is not to be confused with boric acid; while borax is a salt of boric acid, it is not chemically the same as boric acid. This distinction matters for understanding how each behaves in cosmetic formulations.
| Property | Boric Acid | Sodium Borate (Borax) |
| Chemical formula | H₃BO₃ | Na₂B₄O₇·10H₂O (decahydrate) |
| Chemical nature | Weak acid | Salt (sodium salt of boric acid) |
| pH in solution | 4.5-5.0 (weakly acidic) | 9.0-11.0 (highly alkaline) |
| Appearance | White crystalline powder | White crystalline powder |
| Solubility | Moderate in cold water, high in hot water | Good water solubility |
| Primary functions | Preservative, pH adjuster, buffering agent | Emulsifier, pH adjuster, water softener |
The pH difference represents the most significant practical distinction. Borax has similar properties to baking soda, but a higher pH level, with the pH range of borax being about 9 to 11; therefore, it can be a significant skin sensitizer when used in cosmetics.
Quick Comparison Overview
Before examining specific differences, here’s how these compounds stack up across key safety and performance criteria:
| Consideration | Boric Acid | Sodium Borate |
| Skin irritation potential | Mild to moderate at 10% | Moderate at 5% |
| Eye irritation | Mild to moderate | Practically nonirritating |
| Skin absorption (intact) | Poor | Poor |
| Skin absorption (damaged) | Readily absorbed | Readily absorbed |
| pH-related irritation risk | Lower (acidic) | Higher (alkaline) |
| Regulatory status (US) | Approved ≤5% | Approved ≤5% |
| Regulatory status (EU) | Banned in cosmetics | Banned in cosmetics |
| Typical usage levels | 0.1-2.4% | 0.1-3.2% |
Difference 1: Safety Profile and Toxicity
Boric Acid
In a 90-day dermal toxicity study, Boric Acid (25-200 mg/kg/day) was nonirritating and nontoxic when applied to the intact skin of rabbits. When tested at household concentrations, boric acid shows relatively low acute toxicity through skin contact.
Acute studies indicated that, at 10% in water, Boric Acid was mildly or moderately irritating to the skin of rabbits and guinea pigs. The irritation potential increases with concentration, though formulations in personal care products typically use much lower levels.
However, damaged skin changes the equation dramatically. Investigators have reported that Sodium Borate and Boric Acid are poorly absorbed through intact skin; however, both compounds are absorbed through abraded, denuded, or burned skin. Once absorbed systemically, boric acid can accumulate and cause toxicity.
Sodium Borate
A 5% Sodium Borate in water solution was mildly or moderately irritating to the skin of rabbits and guinea pigs, and practically nonirritating when instilled in rabbits’ eyes. The skin irritation profile differs from boric acid, with sodium borate showing irritation at lower concentrations.
In clinical studies, cosmetic formulations containing up to 3.2% Sodium Borate were nonirritating to moderately irritating and nonsensitizing when applied to human skin. Real-world human testing shows variable responses, with some individuals experiencing no issues while others develop irritation.
The alkaline nature creates specific concerns. The cosmetics industry recommends that no borates be used in products designed for use on damaged skin, particularly due to enhanced penetration and the pH-related irritation potential.
Difference 2: Reproductive and Developmental Toxicity
Both compounds share the same critical safety concern that ultimately led to their EU ban.
Reproductive Effects
Doses of up to 1.06 g/kg/day Sodium Borate in the diet of male rats exerted toxic effects on the gonads as well as infertility. These animal studies demonstrated clear reproductive harm at high exposure levels.
High exposure to borax (and boric acid) is believed to disrupt the body’s hormones, with studies showing they may especially impair male reproduction, reducing sperm count and libido. In laboratory animals, both compounds caused testicular atrophy and reduced fertility.
For females, concerns also exist. In women, borax may reduce ovulation and fertility, and in pregnant lab animals, high-level exposures to borax was found to cross the placenta border, harming fetal development and causing low birth weight.
However, context matters. These studies involved oral ingestion or inhalation of substantial quantities. The cosmetic industry’s own safety panel states that these chemicals are unsafe for infant or damaged skin, because they can absorb readily into the body, but topical application to intact adult skin produces minimal systemic absorption.
Regulatory Classification
The EU Cosmetic Regulation was amended on Nov. 27, 2019, to add boric acid, borates, tetraborates, octaborates and boric acid salts and esters to Annex II (Entries 1395 and 1396), the list of substances prohibited in cosmetic products in the EU. This comprehensive ban reflects Europe’s precautionary approach to ingredients showing reproductive toxicity in animal studies.
In the United States, regulations remain less restrictive. The Panel concluded Sodium Borate and Boric Acid, in concentrations less than or equal to 5%, are safe as cosmetic ingredients when used as currently recommended; however, cosmetic formulations containing free Sodium Borate or Boric Acid at this concentration should not be used on infant skin or injured skin.
Difference 3: Functional Uses in Formulations
Boric Acid Applications
Sodium borate and boric acid are used as preservatives to protect cosmetics and personal care products from spoilage, and they are also used as buffering agents to adjust pH and to minimize the change in the pH of a solution when an acid or a base is added.
By implementing boric acid into skincare formulas, personal care products can deter bacteria formation and hinder contamination, thereby prolonging the longevity of products. The antimicrobial properties provide preservation benefits, though boric acid shows weaker bactericidal activity compared to other preservatives like parabens.
Primary Uses:
- Preservative system component (often combined with other preservatives)
- pH buffering in neutral to slightly acidic formulations
- Osmotic pressure regulator in eye-area products
- Viscosity modifier in certain formulations
Sodium Borate Applications
In the skincare world, Borax is often found in creams, lotions, shampoos, gels, bath salts, and bath bombs, and it’s often used to aid in emulsification and preserve products.
Sodium borate and boric acid help to keep an emulsion from separating into its oil and liquid components, making borax particularly valuable in cream and lotion formulations where oil and water phases must remain blended.
Primary Uses:
- Emulsification aid in creams and lotions
- Water softener in bath products
- pH adjustment to alkaline ranges
- Cleansing agent in some formulations
- Buffering agent for alkaline systems
Difference 4: Products Containing These Ingredients
What Has Boric Acid and Sodium Borate in It?
According to 2023 FDA VCRP data, Sodium Borate had 30 reported uses and Boric Acid had 8 reported uses, showing sodium borate appears more frequently in current formulations despite declining overall use.
Products Historically Containing Boric Acid:
- Eye makeup removers and eye lotions
- Face creams and lotions (especially eye contour products)
- Diaper rash creams (though controversial)
- Nail bleaching products
- Deodorant formulations
- Toothpaste formulations
Products Historically Containing Sodium Borate:
- Bath salts and bath bombs
- Shampoos and hair conditioners
- Body lotions and creams
- Bath oils and bubble baths
- Hair straightening products
- Permanent wave solutions
Despite this guidance, boric acid is found in some diaper creams, raising particular concerns given infants’ thinner skin and higher absorption rates.
In 2022, the maximum reported concentration of use for Sodium Borate was 0.78% in other shaving preparations, compared to up to 20% in bath soaps and detergents (which was reported to be diluted to approximately 3% during use) as reported in 2002. Usage has declined substantially over the past two decades as manufacturers reformulate with alternative ingredients.
Difference 5: Regulatory and Market Trends
The regulatory landscape for these ingredients has shifted dramatically, creating divergence between regions.
United States:
- Both ingredients remain approved at ≤5% concentration
- FDA permits use as indirect food additives in specific applications
- Cosmetic ingredient safety panel recommends avoiding on infant or injured skin
- No mandatory labeling warnings required beyond standard ingredient disclosure
European Union:
- Complete ban on boric acid, sodium borate, and related boron compounds in cosmetics
- Ban effective since November 2019
- Classification as reproductive toxicants (Category 1B) drove the prohibition
- No exemptions for low concentrations
Canada: Both the European Union and Canada restrict these ingredients in body care products made for children under three years of age and require that products containing these ingredients be labeled as not appropriate for broken or damaged skin.
Market Response
Manufacturers have mostly eliminated borax and its relative sodium borate from personal care products because the chemicals are easily absorbed through skin. Even in regions where these ingredients remain legal, voluntary reformulation has become common as brands respond to consumer concerns and simplify international product portfolios.
The trend toward “clean beauty” and ingredient transparency has accelerated the phase-out. Many consumers actively avoid products containing boron compounds regardless of regulatory status or concentration levels.
Which One Is Actually Safer?
Neither boric acid nor sodium borate can be declared definitively “safer” than the other. Both present similar reproductive toxicity concerns based on animal studies, both penetrate damaged skin readily, and both have legitimate preservative and functional benefits in formulations.
The practical safety differences relate primarily to:
- pH-related irritation: Sodium borate’s alkaline nature (pH 9-11) makes it more likely to cause irritation on sensitive skin compared to boric acid’s mildly acidic profile
- Skin compatibility: Boric acid may be better tolerated in facial products due to its lower pH matching skin’s natural acidity
- Functional concentration: Sodium borate often requires higher concentrations for emulsification, potentially increasing exposure
For intact adult skin at approved concentrations, both compounds appear relatively safe based on decades of cosmetic use. The concerns emerge with:
- Application to damaged, abraded, or burned skin
- Use on infants and young children
- Products with concentrations approaching the 5% maximum
- Long-term cumulative exposure effects
Sourcing Cosmetic-Grade Boron Compounds
For manufacturers still formulating with boric acid or sodium borate in regions where they remain approved, sourcing pharmaceutical or cosmetic-grade materials with proper documentation is essential. Quality specifications, certificates of analysis, and regulatory compliance documentation support safety validation and regulatory inspections.
Elchemy connects cosmetic manufacturers with qualified suppliers of boric acid, sodium borate, and alternative ingredients for companies reformulating away from boron compounds. Whether you need cosmetic-grade materials meeting FDA or international standards, or assistance identifying safer functional alternatives, we help source ingredients with complete documentation supporting your quality management and regulatory compliance requirements.
Conclusion
Both boric acid and sodium borate served the cosmetics industry effectively for decades as multifunctional ingredients offering preservation, pH control, and formulation benefits. However, reproductive toxicity concerns demonstrated in animal studies have driven regulatory restrictions in Europe and voluntary reformulation in many markets.
For personal care products, neither compound offers compelling safety advantages over the other. Both present similar systemic toxicity risks when absorbed through damaged skin, both warrant avoidance on infant skin, and both face growing consumer resistance regardless of regulatory status. The pH difference makes boric acid slightly preferable for pH-sensitive formulations, while sodium borate’s emulsification properties suit specific cream and lotion applications.
The broader trend points toward eliminating both ingredients from personal care formulations as safer alternatives become available. Companies operating internationally increasingly find it simpler to reformulate once for all markets rather than maintain different formulations based on regional regulations.
