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Head-to-head evidence comparison — which supplement is right for you?
Sunscreen (SPF) wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mostly mechanism / observational
Top outcomes
Verdict
Mostly mechanism / observational
Top outcomes
Shared outcomes (1)
Outcomes where both Glycolic Acid and Sunscreen (SPF) have evidence — compare verdict strength side-by-side.
Topical cosmetic only. Leave-on glycolic acid is used at roughly 5-15% in lotions/serums (often at low pH), applied to clean skin a few nights per week and building as tolerated; professional peels (20-70%) are applied in-office at intervals. There is no oral, injectable, or systemic dose — it is not ingested. Pair with daily sunscreen. This library does not provide an ingestion protocol.
evening
Leave-on lotion or serum (≈5-15% glycolic acid)
Topical OTC. Apply a broad-spectrum SPF 30+ sunscreen daily to sun-exposed skin as the last step of a morning routine, using an adequate amount (about 2 mg/cm² — roughly a nickel-sized dollop for the face, a shot-glass for the body) and reapply every ~2 hours of sun exposure and after swimming/sweating. Mineral (zinc oxide / titanium dioxide) filters are preferred if you're concerned about systemic absorption. There is no oral or systemic dose — it is not ingested. This library does not provide an ingestion protocol.
morning
Broad-spectrum SPF 30+, applied daily; mineral (zinc oxide/titanium dioxide) if concerned about absorption
Throughout
8-12 weeks
8-16 weeks
First weeks
Throughout
Ongoing (years)
Ongoing
Throughout
A double-blind randomized clinical trial on the effectiveness of a daily glycolic acid 5% formulation in the treatment of photoaging.
Dermatol Surg (1998) · Rct · n=75
75 volunteers applied 5% unneutralized glycolic acid cream or placebo to face and neck daily for 3 months (double-blind, randomized, placebo-controlled)
Clinical improvement of photoaged skin with 50% glycolic acid. A double-blind vehicle-controlled study.
Dermatol Surg (1996) · Rct · n=41
41 volunteers received a 50% glycolic acid peel vs vehicle weekly for 4 weeks (in-office peel strength)
Mode of action of glycolic acid on human stratum corneum: ultrastructural and functional evaluation of the epidermal barrier.
Arch Dermatol Res (1997) · Open label
Electron-microscopy study of human skin after 3 weeks of 4% glycolic acid twice daily
Sunscreen and prevention of skin aging: a randomized trial.
Ann Intern Med (2013) · Rct · n=903
Randomized community trial (n=903): the daily sunscreen group showed no detectable increase in photoaging (skin microtopography) after 4.5 years
Molecular mechanisms of photoaging and its prevention by retinoic acid: ultraviolet irradiation induces MAP kinase signal transduction cascades that induce Ap-1-regulated matrix metalloproteinases that degrade human skin in vivo.
J Investig Dermatol Symp Proc (1998) · Review
Mechanistic model: UV activates MAP-kinase pathways and AP-1, which upregulate matrix metalloproteinases (MMPs)
Daily Use of a Facial Broad Spectrum Sunscreen Over One-Year Significantly Improves Clinical Evaluation of Photoaging.
Dermatol Surg (2016) · Open label · n=32
Single-arm prospective study (n=32): broad-spectrum SPF 30 applied daily to the face for 52 weeks
Sunscreen (SPF) has a higher evidence score (9/10 vs 6/10) and wins in 3 of 3 categories.
For reduce wrinkles & fine lines, Sunscreen (SPF) has a higher relevance score (90 vs 55).
No known interactions between Glycolic Acid and Sunscreen (SPF) have been documented in our database. However, always consult a healthcare provider before combining supplements.