Evidence library
Every ingredient story and claim approach on this site is grounded in peer-reviewed human research. Here are the trials CSL scientists cite, each linked to its PubMed or journal record.
Guires Cosmetic Science Lab
Our clinical evidence library: peer-reviewed randomised controlled trials, double-blind studies and systematic reviews behind the cosmetic and personal care ingredients we formulate with.
Start your project with Guires CSLOur evidence standard
We cite studies on people, not only lab or animal data, and prefer randomised, controlled, blinded designs.
Every study is published in a peer-reviewed journal and linked to its PubMed record so you can read it yourself.
We say when a trial is open-label, compares against a medicine, or tests an oral supplement rather than a cosmetic.
Published trials show what an ingredient or approach can do. A finished product still needs its own testing before a claim goes on pack.
Skin care
Randomised, double-blind, vehicle-controlled · 36 older adults · 24 weeks
Fine wrinkling improved significantly vs vehicle (score change −1.64 vs −0.08, P<.001), with increased glycosaminoglycans and procollagen I.
Kafi R et al. Arch Dermatol 2007;143(5):606–612 · PMID 17515510
Double-blind, split-face · 50 women · 12 weeks
Significant reductions in fine lines, wrinkles, spots, red blotchiness and sallowness, and improved elasticity, vs the vehicle side.
Bissett DL et al. Dermatol Surg 2005;31(7 Pt 2):860–865 · PMID 16029679
Vehicle-controlled human trials · 18 and 120 participants
Significantly less hyperpigmentation and lighter-looking skin vs vehicle, visible from 4 weeks.
Hakozaki T et al. Br J Dermatol 2002;147(1):20–31 · PMID 12100180
Double-blind, randomised, split-site · 20 women · 6 months
Clinical photoageing score improved from 6.7 to 4.4 on the treated side, with denser skin microrelief and fewer deep furrows.
Humbert PG et al. Exp Dermatol 2003;12(3):237–244 · PMID 12823436
Randomised, controlled, intra-individual · 76 women · 60 days
All molecular weights improved hydration and elasticity vs vehicle; the low weights (50 and 130 kDa) also reduced wrinkle depth.
Pavicic T et al. J Drugs Dermatol 2011;10(9):990–1000 · PMID 22052267
Double-blind, placebo-controlled, randomised · 24 adults with atopic dermatitis · 4 weeks
Skin hydration rose vs vehicle from week 1 (p<0.0001) and barrier function (TEWL) improved by week 4.
Breternitz M et al. Skin Pharmacol Physiol 2008;21(1):39–45 · PMID 18025807
Double-blind, randomised · 24 adults with dry skin · 28 days + 7-day follow-up
Better hydration, lower TEWL and improved skin pH at every time point, maintained 7 days after stopping.
Lueangarun S et al. Dermatol Ther 2019;32(6):e13090 · PMID 31585489
Randomised, double-blind, placebo-controlled · 75 people with atopic dermatitis · 30 days
Reduced eczema severity (P=0.0044), itch and sleep loss, and lowered S. aureus colonisation vs placebo.
Gueniche A et al. Br J Dermatol 2008;159(6):1357–1363 · PMID 18795916
Randomised, double-blind, intra-individual, multicentre · 65 adults · 28 days
Efficacy and tolerability equivalent to the active comparator on eczema score, global assessment and itch.
Marini A et al. Skin Pharmacol Physiol 2014;27(2):57–65 · PMID 23949258
Randomised community trial, blinded assessment · 903 adults · 4.5 years
Daily users showed 24% less skin ageing (relative odds 0.76) than discretionary users.
Hughes MC et al. Ann Intern Med 2013;158(11):781–790 · PMID 23732711
Randomised, double-blind · 44 adults · 12 weeks
Both reduced wrinkle area and hyperpigmentation with no significant difference; bakuchiol caused less scaling and stinging.
Dhaliwal S et al. Br J Dermatol 2019;180(2):289–296 · PMID 29947134
Sun care
Randomised community trial, blinded assessment · 903 adults · 4.5 years
Daily users showed 24% less skin ageing (relative odds 0.76) than discretionary users.
Hughes MC et al. Ann Intern Med 2013;158(11):781–790 · PMID 23732711
Randomised trial · 1,621 adults · 4.5 years + 10-year follow-up
Invasive melanomas were fewer with daily use (3 vs 11; HR 0.27, 95% CI 0.08–0.97); all new primary melanomas halved (11 vs 22), borderline significant.
Green AC et al. J Clin Oncol 2011;29(3):257–263 · PMID 21135266
Community randomised factorial trial · 1,621 adults · 4.5 years
Squamous cell carcinoma tumours were 39% lower with daily sunscreen (RR 0.61, 95% CI 0.46–0.81); no effect on basal cell carcinoma.
Green A et al. Lancet 1999;354(9180):723–729 · PMID 10475183
Randomised, placebo-controlled · 588 adults aged 40+ · one summer
Fewer new solar keratoses with sunscreen (1.6 vs 2.3 per person), and more existing lesions went into remission.
Thompson SC et al. N Engl J Med 1993;329(16):1147–1151 · PMID 8377777
Randomised, double-blind · 87 young adults · summer holiday
People used the same amount of sunscreen but stayed in the sun longer with SPF 30 (72.6 vs 58.2 hours), a reason to design for real use.
Autier P et al. J Natl Cancer Inst 1999;91(15):1304–1309 · PMID 10433619
In-vivo SPF study · 20 volunteers
Protection fell steeply below the 2 mg/cm² test dose, so texture that encourages generous use matters as much as the SPF number.
Faurschou A, Wulf HC. Br J Dermatol 2007;156(4):716–719 · PMID 17493070
Randomised, double-blind · 68 patients with melasma · 8 weeks
The iron-oxide formula improved melasma severity by 15% more than the UV-only sunscreen (MASI), with lower melanin on biopsy.
Castanedo-Cazares JP et al. Photodermatol Photoimmunol Photomed 2014;30(1):35–42 · PMID 24313385
Randomised comparative trial · 40 patients · 6 months
Melasma relapsed far less with the tinted, visible-light formula (median MASI rise 0.45 vs 2.43, P=.027).
Boukari F et al. J Am Acad Dermatol 2015;72(1):189–190 · PMID 25443629
Double-blind crossover · 38 people prone to cold sores
UV-triggered cold sores appeared in 71% after placebo and in none after sunscreen.
Rooney JF et al. Lancet 1991;338(8780):1419–1422 · PMID 1683420
Hair & scalp care
Randomised, double-blind, placebo-controlled · 144 women with self-perceived thinning · 8 weeks
Significant increase in hair amount vs placebo on phototrichogram; the shampoo also lowered scalp oxidative-stress markers and TEWL.
Davis MG et al. Int J Cosmet Sci 2021;43(Suppl 1):S26–S33 · PMID 34424549
Randomised, open-label, multicentre non-inferiority · 210 men · 6 months
Proportion of hairs in the growth phase rose 10.6% with caffeine vs 11.7% with minoxidil, meeting the non-inferiority margin.
Minoxidil is a medicine; it appears here only as the comparator.
Dhurat R et al. Skin Pharmacol Physiol 2017;30(6):298–305 · PMID 29055953
Randomised comparative trial · 100 men · 6 months
Hair count rose significantly in both groups with no difference between them; scalp itching was less frequent with rosemary.
Active-comparator trial, not placebo-controlled.
Randomised, placebo-controlled · 60 men with moderate–severe dandruff · 56 days
Loose and adherent flakes, redness and overall clinical score improved significantly vs placebo, with a rebalanced scalp microbiota.
Oral supplement (nutricosmetic).
Reygagne P et al. Benef Microbes 2017;8(5):671–680 · PMID 28789559
Randomised, double-blind, placebo-controlled · 60 women · 90 days
Terminal hair count increased significantly vs placebo (P<0.0001), with less shedding and better self-assessed quality of life.
Oral supplement (nutricosmetic).
Ablon G. Dermatol Res Pract 2015;2015:841570 · PMID 25883641
Randomised, double-blind, placebo-controlled · 76 men · 24 weeks
Mean hair count rose 40% vs 10% with placebo (P<0.001).
Oral supplement; the test product was a branded capsule.
Cho YH et al. Evid Based Complement Alternat Med 2014;2014:549721 · PMID 24864154
Body wash & body care
Double-blind, placebo-controlled, randomised · 24 adults with atopic dermatitis · 4 weeks
Skin hydration rose vs vehicle from week 1 (p<0.0001) and barrier function (TEWL) improved by week 4.
Breternitz M et al. Skin Pharmacol Physiol 2008;21(1):39–45 · PMID 18025807
Double-blind, randomised · 24 adults with dry skin · 28 days + 7-day follow-up
Better hydration, lower TEWL and improved skin pH at every time point, maintained 7 days after stopping.
Lueangarun S et al. Dermatol Ther 2019;32(6):e13090 · PMID 31585489
Controlled crossover · 10 adults · consecutive 4-week periods
Skin pH was higher with soap (p<0.01) and propionibacteria counts rose markedly, showing how cleanser pH shifts skin flora.
Korting HC et al. Acta Derm Venereol 1987;67(1):41–47 · PMID 2436413
Open, randomised, controlled · 40 infants
Alkaline soap raised skin pH most (+0.45 vs +0.19 for water) and removed the most surface lipid; syndets were gentler.
Gfatter R et al. Dermatology 1997;195(3):258–262 · PMID 9407174
Assessor-blinded, randomised non-inferiority · 307 newborns · 14–28 days
The wash was non-inferior to water on TEWL (12.8 vs 12.5 g/m²/h) and gave higher skin hydration (p=0.022).
Lavender T et al. J Obstet Gynecol Neonatal Nurs 2013;42(2):203–214 · PMID 23421327
Randomised, single-blind crossover · 42 children · 2 × 2 weeks
Eczema severity (SCORAD) fell by 21 points more with frequent bathing followed by moisturiser.
Cardona ID et al. J Allergy Clin Immunol Pract 2020;8(3):1014–1021 · PMID 31733336
Randomised, double-blind · 197 adults with atopic dermatitis · 30 days
Both relieved dryness equally; the glycerin cream caused less stinging (10% vs 24% moderate–severe).
Lodén M et al. Acta Derm Venereol 2002;82(1):45–47 · PMID 12013198
Double-blind, vehicle-controlled studies · 169 adults · 2 weeks
Hydration rose and TEWL fell significantly vs vehicle and untreated skin; the richer lotion still moisturised 6 days after stopping.
Weber TM et al. J Clin Aesthet Dermatol 2012;5(8):29–39 · PMID 22916312
Controlled four-group trial · 200 adults
Both scents lowered anxiety and improved mood compared with no scent.
Lehrner J et al. Physiol Behav 2005;86(1–2):92–95 · PMID 16095639
Personal care & hygiene
Randomised split-axilla · 19 adults · gravimetric sweat test
The aluminium chloride side sweated significantly less than the comparison side (p=0.0002), showing how gravimetric testing separates actives.
Small study; 20% aluminium chloride is prescription strength in some markets.
Experimental study · 17 adults · 8 days · culture and 16S sequencing
Antiperspirant sharply reduced underarm bacterial density, and product users had a different bacterial community from non-users.
Not randomised; no odour endpoint.
Prospective comparison · 32 nurses · 6 weeks
Irritation and dryness rose substantially with soap and water but changed little with the alcohol gel, confirmed by skin-water measurements.
Boyce JM et al. Infect Control Hosp Epidemiol 2000;21(7):442–448 · PMID 10926393
Double-blind repeated application · 35 adults · 2 weeks
Redness and dryness scores were lower with the emollient-containing rub (P=0.022).
Kampf G et al. Contact Dermatitis 2005;53(6):344–349 · PMID 16364124
Randomised controlled · 129 office workers · 12 months
Colds (OR 0.35), fever (OR 0.38) and cough (OR 0.45) were all less frequent, with fewer days of illness.
Cluster-randomised · 24 day-care centres, 911 children · 8 months
The sanitiser group had 23% fewer respiratory infections and 31% fewer antibiotic prescriptions than control.
Azor-Martinez E et al. Pediatrics 2018;142(5):e20181245 · PMID 30297500
Systematic review and meta-analysis · 30 studies
Better hand hygiene cut gastrointestinal illness by 31% and respiratory illness by 21%; education with plain soap gave the largest benefit.
Four-arm randomised · 1,020 metalworkers · 12 months
Skin worsened in controls, while combined skin care and protection creams gave the largest improvement.
Kütting B et al. Br J Dermatol 2010;162(2):362–370 · PMID 19804591
Cluster-randomised · 19 wards, 501 workers · 12 months
No significant difference in hand-eczema severity overall, though mild cases improved more, showing that access alone is not enough.
Primary endpoint not significant.
Soltanipoor M et al. Contact Dermatitis 2019;80(6):365–373 · PMID 30652317
Randomised, double-blind, placebo-controlled · 167 people with diabetes · 4 weeks
Deep open heel fissures remained in 6% vs 24% with placebo (P=0.002), and dryness improved more with the test cream.
Gin H et al. Diabet Med 2017;34(9):1309–1317 · PMID 28627029
Systematic review and meta-analysis · 12 RCTs, 603 participants
Urea creams outperformed standard base creams for dryness at 4 weeks, with high-certainty evidence.
Borgström K et al. Front Clin Diabetes Healthc 2026;7:1922860
Open, gynaecologist-supervised · 36 women · 28 days
No increase in dryness, redness, itch or stinging; moisturisation rose and the vulvar microbiome was unchanged.
No control group; manufacturer-affiliated authors.
Controlled comparison · 31 women · 4 weeks
The 2% formula significantly reduced lip roughness at 2 and 4 weeks and improved barrier function.
Tamura E et al. Int J Cosmet Sci 2021;43(2):158–164 · PMID 33258166
Colour cosmetics
Randomised, double-blind · 68 patients with melasma · 8 weeks
The iron-oxide formula improved melasma severity by 15% more than the UV-only sunscreen (MASI), with lower melanin on biopsy.
Castanedo-Cazares JP et al. Photodermatol Photoimmunol Photomed 2014;30(1):35–42 · PMID 24313385
Randomised comparative trial · 40 patients · 6 months
Melasma relapsed far less with the tinted, visible-light formula (median MASI rise 0.45 vs 2.43, P=.027).
Boukari F et al. J Am Acad Dermatol 2015;72(1):189–190 · PMID 25443629
Double-blind crossover · 38 people prone to cold sores
UV-triggered cold sores appeared in 71% after placebo and in none after sunscreen.
Rooney JF et al. Lancet 1991;338(8780):1419–1422 · PMID 1683420
Controlled comparison · 50 women with acne · 4 weeks
Makeup did not slow acne improvement, and the makeup group gained more on quality-of-life scores.
Matsuoka Y et al. J Dermatol 2006;33(11):745–752 · PMID 17073988
Before/after cohort · 78 people with vitiligo
Dermatology quality-of-life score improved from 7.3 to 5.9 (P=.006), mainly on self-consciousness and clothing choices.
No separate control group.
Ongenae K et al. Dermatology 2005;210(4):279–285 · PMID 15942213
International observational study · 1,840 people · 4–6 weeks
Skin-related quality of life improved on every domain (P<0.0001).
No control group; industry-sponsored.
Cristea A et al. Clin Cosmet Investig Dermatol 2020;13:253–257 · PMID 32280256
Men's grooming
Randomised, double-blind, placebo-controlled · 100 adults · 4 weeks (plus a 30-person split-face study)
Sebum excretion fell significantly vs placebo at 2 and 4 weeks; casual sebum also fell in the split-face study.
Draelos ZD et al. J Cosmet Laser Ther 2006;8(2):96–101 · PMID 16766489
Randomised, three parallel groups · 90 men with razor bumps · 12 weeks
The advanced daily regimen improved itching (P=.002) and perceived results; shaving less often reduced ingrown hairs.
Daniel A et al. J Drugs Dermatol 2013;12(4):410–418 · PMID 23652888
Within-subject comparison with near-infrared imaging · 59 men
Redness right after shaving was lower with the single-blade razor (40% vs 58%), showing how imaging can quantify shave comfort.
Not randomised; shown as a method example.
Boodoo et al. Skin Res Technol 2024;30:e13598 · PMID 38279588
Randomised, evaluator-blind · 133 adults with acne · 21 days
The new washes were as well tolerated as the reference, with no meaningful change in irritation scores.
Benzoyl peroxide acne washes are OTC drugs in the US and medicines in the EU.
Santos-Caetano JP, Cargill MR. J Drugs Dermatol 2019;18(4):350–356
Baby & kids
Open, randomised, controlled · 40 infants
Alkaline soap raised skin pH most (+0.45 vs +0.19 for water) and removed the most surface lipid; syndets were gentler.
Gfatter R et al. Dermatology 1997;195(3):258–262 · PMID 9407174
Assessor-blinded, randomised non-inferiority · 307 newborns · 14–28 days
The wash was non-inferior to water on TEWL (12.8 vs 12.5 g/m²/h) and gave higher skin hydration (p=0.022).
Lavender T et al. J Obstet Gynecol Neonatal Nurs 2013;42(2):203–214 · PMID 23421327
Randomised, assessor-blinded · 124 high-risk newborns · 6 months
Eczema at 6 months was 22% vs 43% (RR 0.50).
Small trial; larger trials below did not confirm prevention.
Simpson EL et al. J Allergy Clin Immunol 2014;134(4):818–823 · PMID 25282563
Randomised · 118 high-risk newborns · 32 weeks
About 32% fewer moisturised infants developed eczema by week 32 (P=.012).
Horimukai K et al. J Allergy Clin Immunol 2014;134(4):824–830 · PMID 25282564
Multicentre, pragmatic · 1,394 newborns · 2 years
No reduction in eczema at age 2 (23% vs 25%), and more skin infections in the emollient group.
Negative trial: we do not claim emollients prevent eczema.
Chalmers JR et al. Lancet 2020;395(10228):962–972 · PMID 32087126
Cluster-randomised factorial · 2,397 newborns · 12 months
Skin care did not reduce atopic dermatitis (11% vs 8%).
Negative trial.
Skjerven HO et al. Lancet 2020;395(10228):951–961 · PMID 32087121
Assessor-blinded equivalence trial · 280 newborns · 4 weeks
Wipes were equivalent to water on skin hydration, and mother-reported nappy rash was lower with wipes (p=0.025).
Industry-funded.
Randomised, assessor-blinded pilot · 115 newborns · 4 weeks
Both oils raised hydration but gave less improvement in skin lipid structure than no oil, a reason to test oils carefully on newborn skin.
Split-side comparison · 46 children with nappy rash · 7 days
Barrier function (TEWL) was better on the treated side by day 3 (p=0.002); severity scores did not differ.
Wananukul S et al. J Med Assoc Thai 2006;89(10):1654–1658 · PMID 17128840
Randomised, double-blind · 117 children · 8 weeks
Eczema severity fell 68% with coconut oil vs 38% with mineral oil (P<0.05).
Evangelista MT et al. Int J Dermatol 2014;53(1):100–108 · PMID 24320105
Randomised, double-blind, active-controlled · children with eczema · 3 weeks
The oatmeal cream matched the prescription barrier cream on eczema improvement, with similar tolerability.
Manufacturer-sponsored.
Lisante TA et al. J Dermatolog Treat 2017;28(7):659–667 · PMID 28366039
Clean, natural & Ayurvedic
Randomised, double-blind · 44 adults · 12 weeks
Both reduced wrinkle area and hyperpigmentation with no significant difference; bakuchiol caused less scaling and stinging.
Dhaliwal S et al. Br J Dermatol 2019;180(2):289–296 · PMID 29947134
Randomised, double-blind · 117 children · 8 weeks
Eczema severity fell 68% with coconut oil vs 38% with mineral oil (P<0.05).
Evangelista MT et al. Int J Dermatol 2014;53(1):100–108 · PMID 24320105
Randomised, double-blind, active-controlled · children with eczema · 3 weeks
The oatmeal cream matched the prescription barrier cream on eczema improvement, with similar tolerability.
Manufacturer-sponsored.
Lisante TA et al. J Dermatolog Treat 2017;28(7):659–667 · PMID 28366039
Randomised, single-blind · 124 people with acne · 3 months
Both reduced lesions significantly; tea tree worked more slowly but caused fewer side effects.
Bassett IB et al. Med J Aust 1990;153(8):455–458 · PMID 2145499
Controlled three-group trial · 90 adults with eczema · 2 weeks
The 2% gel reduced redness, swelling and itch more than the 1% gel.
Saeedi M et al. J Dermatolog Treat 2003;14(3):153–157 · PMID 14522625
Halal cosmetics
Analytical method validation · market samples
Detection limit 1,316 pg DNA with 101% amplification efficiency; none of the tested face masks contained porcine DNA.
Rumiyati R et al. Open Vet J 2026;16(1):478–491 · PMID 42375310
Narrative review
LC-MS/MS performs best in complex cosmetic matrices; PCR and ELISA are limited when DNA or protein markers degrade in processing.
Analytical comparison · 9 products
The two methods agreed on only 44% of samples, so combining methods gives more reliable screening.
Small sample.
Cross-sectional survey · 289 women in Indonesia
Promotion, attitude and perceived control predicted purchase intention; the halal logo alone did not.
Oral care
Cochrane network meta-analysis · 96 RCTs · ~65,000 participants
1,450–1,500 ppm fluoride clearly reduced decay vs non-fluoride paste in children and adolescents, and slightly outperformed 1,000–1,250 ppm.
Walsh T et al. Cochrane Database Syst Rev 2019;3:CD007868 · PMID 30829399
Randomised, double-blind non-inferiority · 194 adults · 18 months
No caries increase in 89% (hydroxyapatite) vs 87% (fluoride); hydroxyapatite was non-inferior.
Co-authors linked to a manufacturer.
Randomised, examiner-blind · 130 adults · 3 weeks
Gum bleeding was 29% lower than control at week 3 (p<0.0001).
Industry-funded.
Acherkouk A et al. BMC Oral Health 2021;21:441 · PMID 34511098
Randomised, double-blind, three-arm · 118 adults · 8 weeks
Air-blast sensitivity fell 70% vs negative control and 50% vs the potassium regimen.
Regimen included a mouthwash.
Cochrane systematic review · 6 trials pooled
Tactile/air-blast sensitivity improved at 6–8 weeks, but self-reported benefit was not significant.
Poulsen S et al. Cochrane Database Syst Rev 2006;(3):CD001476 · PMID 16855970
Randomised, double-blind, placebo-controlled · 40 adults · 6 weeks
Tooth yellowness fell significantly more than placebo by week 2 (p<0.001), with continued gains to week 6.
6% peroxide is dentist-only in the EU; consumer products are limited to 0.1%.
Randomised, placebo-controlled · 139 adults · 6 months
15% less gum inflammation, 33% less bleeding and 16% less plaque than placebo.
Industry-sponsored.
Mankodi S et al. Am J Dent 2005;18(Spec No):9A–14A · PMID 16178130
Cochrane systematic review · 10 studies · 5,903 participants
Fluoride toothpaste with 10% xylitol may reduce caries by 13% more than fluoride alone; evidence is low certainty.
Riley P et al. Cochrane Database Syst Rev 2015;(3):CD010743 · PMID 25809586
Systematic review and meta-analysis · 24 RCTs
Herbal toothpaste reduced plaque more at 4 weeks, but showed no advantage for gum health or over fluoride toothpaste.
Janakiram C et al. BMC Complement Med Ther 2020;20:43 · PMID 32046707
Examiner-blind crossover · 75 adults · 1 week
Odour-causing sulphur gases were lower at every point up to 12 hours (p<0.0001), down 91% immediately after brushing.
Industry study.
Payne D et al. Int Dent J 2011;61(Suppl 3):60–66 · PMID 21762157
These are published studies on ingredients, methods and routines, not on products we have made. A finished product needs its own testing before a claim goes on pack, and we design that study with you.
Start a project
Our formulation chemists, testing scientists and regulatory specialists work alongside your team, from the first brief to a market-ready product. Bring a brief, a benchmark or just an idea: a scientist will reply within one working day with next steps and an indicative scope.