The Index · Vitamin C phosphate salt
Sodium ascorbyl phosphate
Sodium Ascorbyl Phosphate
Stable vitamin C derivative with surprisingly decent acne data; weaker than L-ascorbic for photoageing.
ModerateSome controlled trials
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Sodium ascorbyl phosphate is ascorbic acid with a phosphate group on the 2-position, which blocks oxidation until skin phosphatases remove it. The trade: it is stable at neutral pH, but conversion is incomplete and the photoageing evidence is much thinner.
The evidence
Where SAP is unexpectedly interesting is acne. A 12-week randomised, double-blind trial of 5 % SAP lotion reduced inflammatory lesions significantly versus vehicle[1], with earlier work showing antimicrobial activity against C. acnes and reduced sebum oxidation[2].
Use it if L-ascorbic acid stings or oxidises before you finish the bottle. Don't expect the same collagen results.
Evidence by claim
Graded separately; the entry grade is the best-supported claim
Converts to ascorbic acid in skin and improves photodamage[2]
LimitedSafety & limits
Source and region, always
all — No restrictions. Stable at neutral pH, so much less likely to sting than L-ascorbic acid. CA US EU UK
Sources · 2
Numbered as cited in the text
- [1]Woolery-Lloyd H, Baumann L, Ikeno H. Sodium L-ascorbyl-2-phosphate 5% lotion for the treatment of acne vulgaris: a randomized, double-blind, controlled trial. Journal of Cosmetic Dermatology (2010)doi:10.1111/j.1473-2165.2010.00480.x
- [2]Klock J, Ikeno H, Ohmori K, et al.. Sodium ascorbyl phosphate shows in vitro and in vivo efficacy in the prevention and treatment of acne vulgaris. International Journal of Cosmetic Science (2005)doi:10.1111/j.1467-2494.2005.00265.x
Revision history
16 Sept 2026Entry createdTheSkindex Desk