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18 claims · 19 studies · 7 synthesized.
C2-7
In cultured melanocytes and keratinocyte-melanocyte models, tranexamic acid reduces melanin content, tyrosinase activity and tyrosinase protein by acting on signalling upstream of the enzyme, rather than being characterised as a direct tyrosinase-enzyme inhibitor. It does so both through a keratinocyte paracrine route (tranexamic acid raised keratinocyte TGF-beta1, which suppressed melanogenesis in melanocytes) and directly on melanocytes (ERK-MITF degradation; cAMP-PKA-CREB-MITF; VEGF-receptor signalling). The evidence is in vitro; in a 30-patient refractory-melasma series, oral tranexamic acid was followed by lower epidermal pigmentation and Melan-A staining.
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Kim MS, Bang SH, Kim JH, Shin HJ, Choi JH, Chang SE. Ann Dermatol 2015;27(3):250-6. PMID 26082580
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Xing X, Xu Z, Chen L, Jin S, Zhang C, Xiang L. Exp Dermatol 2021 Dec 17;31(4):633-640. PMID 34862827
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Bae YJ, Lee EJ, Kim JY, Park S, Hwang S, Kwon IJ, Alqahtani JM, Oh SH. Exp Dermatol 2025;34(12):e70194. PMID 41392597
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Zhu JW, Ni YJ, Tong XY, Guo X, Wu XP, Lu ZF. Int J Med Sci 2020;17(7):903-911. PMID 32308543
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Nagaraju D, Bhattacharjee R, Vinay K, Saikia UN, Parsad D, Kumaran MS. Dermatol Ther 2018;31(5):e12704. PMID 30253023
C5-1
Hard water dramatically increases barrier damage from surfactant cleansers — calcium/magnesium ions bind to surfactants and remain on skin after rinsing.
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The record
The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects.
C5-2
Skin surface pH averages ~4.7-5.5; acidic pH keeps resident flora attached, alkaline disperses it; below-5 skin is in better barrier condition.
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The record
Natural skin surface pH is on average below 5, which is beneficial for its resident flora.
C10-3
Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.
Verified
C13-4
Skin pH rises after a single wash and takes hours to recover; soap causes the greatest pH rise of any cleanser type tested.
Verified
C14-4
Skin's optimal surface pH sits around 4.5-5.5; a single alkaline exposure measurably raises pH and recovery takes hours.
Verified
C25-1
Ambient humidity and temperature strongly affect the stratum corneum; colder/drier regions show markedly higher population-level dry-skin burden than warm/humid ones.
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Climate, Humidity, and Population-Level Interest in Dry Skin: Infodemiology Analysis Using Google Trends Across the United States.
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Ambient humidity and the skin: the impact of air humidity in healthy and diseased states.
C25-2
Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface.
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The record
Effects of water activity and low molecular weight humectants on skin permeability and hydration dynamics - a double-blind, randomized and controlled study.
C27-2
Skin's acidic pH supports barrier repair and antimicrobial defense; pH stays raised for hours after even a single wash.
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C34-1
Skin surface pH rises after a single wash, even water alone; recovery takes up to several hours.
VerifiedOne source behind this claim
C34-5
In elderly dry skin, high TEWL tracks high pH, low hydration, low surface lipid.
VerifiedOne source behind this claim
CFRAG-1
The EU Cosmetics Regulation (EC No 1223/2009, Annex III) requires named fragrance allergens — historically 26, including linalool, limonene, citronellol, geraniol and eugenol — to be individually declared on cosmetic ingredient labels when present above 0.001% in leave-on or 0.01% in rinse-off products; Commission Regulation (EU) 2023/1545 (26 Jul 2023) expands the declarable list to 80+ substances (compliance deadlines Jul 2026 / Jul 2028). A 'fragrance-free' claim does not preclude these compounds appearing on-label under their own names.
Verified
CLIPID-1
Triterpene constituents of shea butter's unsaponifiable fraction have anti-inflammatory activity.
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The record
Akihisa T, Kojima N, Kikuchi T, Yasukawa K, Tokuda H, T Masters E, Manosroi A, Manosroi J. J Oleo Sci 2010;59(6):273-80. PMID 20484832
CLIPID-2
Shea butter is a component of evidence-backed eczema barrier formulations.
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The record
Micali G, Paternò V, Cannarella R, Dinotta F, Lacarrubba F. G Ital Dermatol Venereol 2018 Jan;153(3):396-402. PMID 29368843
CLIPID-3
Traditional wound-healing use of shea butter is documented.
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The record
Anyanwu EG, Onuchukwu CL, Ojukwu CP, Anyanwu CN. J Ethnopharmacol 2026 Jan;361:121293. PMID 41619863
CMIST-2
The water-transport resistance of a deposited occlusive or emulsion film can increase stratum-corneum hydration and alter permeability and TEWL; the relevant mechanism is the film left on skin.
Verified
CPAN-1
Panthenol (pro-vitamin B5) accelerates post-procedure skin barrier recovery, reduces transepidermal water loss, and improves stratum corneum moisture and barrier markers.
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VerifiedOne of 2 sources behind this claim · see the other
CSHEA-2
No study located shows shea BUTTER fades hyperpigmentation: the published melanogenesis-inhibition result is for a lab extract of the defatted kernel, not the butter; the Library declines the "shea fades dark spots" claim.
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The record
Zhang J, Kurita M, Shinozaki T, Ukiya M, Yasukawa K, Shimizu N, Tokuda H, Masters ET, Akihisa M, Akihisa T. Phytochemistry 2014 Oct;108:157-70. PMID 25446237
RBAR-1
A thinned barrier lipid layer plausibly lets water leave faster and lets irritants in more easily; extrapolated from ceramide-profile/barrier-function evidence and the experimental barrier-disruption + UV pigmentation finding; C25-4 is Unconfirmed.
SYNTHESIZED
Synthesized from:
- C29-3 Ceramide subclass composition is tightly linked to barrier function; a skewed or altered ceramide profile correlates with barrier dysfunction. DOI
- CPEEL-9 Experimentally disrupting the epidermal barrier via tape stripping before UV exposure produces significantly more pronounced, longer-lasting pigment darkening and (after UVB) more pronounced delayed erythema and PIH than intact-barrier skin, scaling with barrier-damage severity.
RBAR-2
For skin of color with documented low upper-layer ceramide and prominent xerosis, topical ceramide- or urea-based moisturizers are a reasonable direct response; extrapolated from low-ceramide findings and the barrier-repair evidence; no trial of ceramide top-up specifically in Fitzpatrick IV-VI.
SYNTHESIZED
Synthesized from:
- C29-1 African American skin was characterized by low ceramide levels in the uppermost layers of the stratum corneum, interpretable alongside the high prevalence of xerosis in Black skin. DOI
- C31-10 African American skin is characterized by low ceramide levels and high protein cohesion in the uppermost stratum corneum, interpreted in relation to the high prevalence of xerosis. PMID 20654785 DOI
- C28-2 Evidence-based skin repair rests on gentle pH-balanced cleansing, ceramide- or urea-based moisturizers, and photoprotection. DOI
- C29-3 Ceramide subclass composition is tightly linked to barrier function; a skewed or altered ceramide profile correlates with barrier dysfunction. DOI
RBAR-3
Oils and butters act mainly as occlusives that slow evaporation of water already in the skin and do not add water; applied to dry skin without a humectant or water they may seal dryness in. Extrapolated from the humectant/occlusive mechanism.
SYNTHESIZED
Synthesized from:
- C25-2 Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface. PMID 24786192 DOI
RBAR-4
Applying a humectant (urea, glycerin) or working the next step into damp skin first, then an occlusive over it, is a reasonable order that follows from the humectant and occlusive mechanisms; no trial of the sequence in Fitzpatrick IV-VI.
SYNTHESIZED
Synthesized from:
- C25-2 Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface. PMID 24786192 DOI
- CJOJ-1 Jojoba oil (Simmondsia chinensis seed oil) has documented anti-inflammatory and wound-healing activity and functions as a wax-ester sebum-mimetic rather than a true triglyceride oil. PMID 24442052 PMID 29280987
RBAR-5
Sealing harder with an occlusive over a humectant in cold dry air and going lighter in hot humid air follows from climate effects on stratum-corneum hydration; no trial of climate-adjusted routines.
SYNTHESIZED
Synthesized from:
- C25-1 Ambient humidity and temperature strongly affect the stratum corneum; colder/drier regions show markedly higher population-level dry-skin burden than warm/humid ones. PMID 42184334 PMC13200769 DOI PMID 27306376 DOI
- C25-2 Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface. PMID 24786192 DOI
RBAR-6
A breached barrier plausibly lets irritants in, and the resulting inflammation drives pigment overproduction on skin of color; stands on the injury->melanocyte pathway and the experimental barrier-disruption + UV finding; the barrier-admits-irritants row is Unconfirmed.
SYNTHESIZED
Synthesized from:
- CPEEL-12 Injury or irritation to keratinocytes (from a peel, tape, or other insult) triggers inflammatory cytokine/interleukin release that stimulates neighboring melanocytes to produce more melanin — the general pathway connecting irritation of any kind to increased pigment.
- C8-3 The core PIH mechanism (melanocytes overproduce pigment in response to inflammation on elevated-melanin-density skin). PMID 21348540 DOI
- CPEEL-9 Experimentally disrupting the epidermal barrier via tape stripping before UV exposure produces significantly more pronounced, longer-lasting pigment darkening and (after UVB) more pronounced delayed erythema and PIH than intact-barrier skin, scaling with barrier-damage severity.
RBAR-7
Layering several strong actives or using sharp-particle scrubs adds irritant and mechanical injury; because irritation can trigger PIH on skin of color, starting low and titrating is the clinical approach.
SYNTHESIZED
Synthesized from:
- C21-6 On skin of color, irritation itself can trigger PIH; clinical approach is to start low and titrate up. PMID 15113286 DOI PMID 35720053 PMC9165627 DOI
- C24-2 In skin of color, acne treatment must balance efficacy against irritation, because irritation itself triggers PIH; treat early, titrate gently. PMID 35720053 PMC9165627 DOI PMID 20725554 PMC2921758
- CPEEL-12 Injury or irritation to keratinocytes (from a peel, tape, or other insult) triggers inflammatory cytokine/interleukin release that stimulates neighboring melanocytes to produce more melanin — the general pathway connecting irritation of any kind to increased pigment.