Sodium Chloride
Also known as Salt, Table Salt, NaCl, Sea Salt, Rock Salt
“No regulator has issued a verdict on this ingredient.”
Sodium chloride (NaCl; CAS 7647-14-5) is a ubiquitous cosmetic excipient used primarily to adjust viscosity, osmolality, and ionic strength in rinse-off and leave-on formulations. CIR has not published a standalone safety assessment for sodium chloride; it is absent from the CIR Quick Reference Table (QRT-122017revised072018), likely because the ingredient is considered an endogenous human electrolyte with a fundamentally understood safety profile. Matthias et al. (Sci Transl Med 2019; PMID 30787167) demonstrated that sodium chloride potently promotes TH2 cell responses and that atopic dermatitis lesional skin exhibits elevated sodium — a mechanistic finding indicating NaCl is not immunologically inert in the skin microenvironment at elevated concentrations. Hagstroemer et al. (Skin Pharmacol 2001; PMID 11174088) found that a moisturizer containing both urea and sodium chloride was somewhat more effective than one without NaCl in atopic dermatitis patients, with improved electrical impedance measurements. El-Amawy and Sarsik (J Cosmet Dermatol 2021; PMID 33098717) reviewed dermatological uses of saline, finding it broadly well-tolerated as a diluent, irrigant, and topical agent across clinical contexts. At typical cosmetic use concentrations (0.5–3%), sodium chloride is considered non-irritating and non-sensitizing; at high concentrations it is hypertonic and may disrupt skin barrier function.
Ubiquitous, well-tolerated excipient used to adjust viscosity and osmolality in topical formulations across all product categories
Hagstroemer et al. 2001 found NaCl improved moisturization efficacy (electrical impedance) in a urea-containing atopic dermatitis cream vs urea alone
Isotonic saline (0.9% NaCl) is extensively used in wound irrigation and dermatological procedures with a well-established tolerability profile (El-Amawy 2021)
Endogenous electrolyte present in all human body fluids; systemic toxicity via topical exposure is not a credible concern at cosmetic use levels
- · Hypertonic concentrations (above physiological ~0.9%) may impair skin barrier function and increase transepidermal water loss — a formulation concern at high doses
Matthias et al. 2019 showed elevated NaCl in the atopic skin microenvironment drives TH2 immune polarization via osmosensitive pathways, raising mechanistic concern that high topical NaCl could exacerbate atopic dermatitis in susceptible individuals
CIR has not formally assessed sodium chloride as a standalone cosmetic ingredient; the absence of a CIR QRT entry means there is no peer-reviewed regulatory safety determination specific to cosmetic use concentrations