Check us against the evidence.

52% of people who quit acne treatment quit for ineffectiveness, within 3 months.

Malassezia folliculitis present in 28.8% of clinically-diagnosed acne.

MF commonly misdiagnosed as acne, persists on acne meds, associated with antibiotic use.

MF mimicry leads to inappropriate antibiotic use.

Acne = loss of C. acnes phylotype balance + dysbiosis, not hyperproliferation; antibiotics induce dysbiosis.

IA1 phylotype biofilm + increased antibiotic tolerance.

Pre/pro/postbiotic systematic review: postbiotic reduces lesions more than control but between-group difference nonsignificant; adjuncts only.

BP vehicle irritancy (surfactants/preservatives/alcohols); low-% formula without them well-tolerated.

Azelaic acid — 4 mechanisms (antimicrobial, tyrosinase inhibition, free-radical scavenging, reduced neutrophil ROS).

Azelaic acid also keratolytic.

Azelaic acid probably less effective than benzoyl peroxide on PGA (Cochrane RR 0.82).

Azelaic acid is first-line topical alongside retinoids and BP.

Azelaic acid antifungal activity + exploratory support in seborrheic dermatitis (Malassezia-driven).

Hidradenitis suppurativa >3x more prevalent in Black vs White; more severe, longer diagnostic delay.

An open-label randomized trial of an at-home 660-nm red/415-nm blue LED device for mild-to-moderate inflammatory acne found significant inflammatory-lesion reduction at 4 and 8 weeks; total-lesion reduction was significant with the red/blue device but not the blue-only comparator, and there was no significant between-group difference for total, inflammatory, or noninflammatory lesion reduction.

FDA 510(k) K210948 describes Omnilux CLEAR as an over-the-counter mask intended to emit red and blue LED energy for mild-to-moderate acne vulgaris of the face; the FDA comparison table lists approximately 630-nm red and 412.5-nm blue wavelengths.

A clay mask formulated with kaolin and bentonite, used twice weekly for 4 weeks by 75 adults with oily/combination skin, produced significant improvements in acne lesion counts, sebum content, stratum corneum hydration, and TEWL, with reduced dryness/irritation and high self-reported tolerability; pore area and porphyrin area did not change significantly.

A single-session 30% salicylic acid peel performed equally to Jessner's solution for acne and post-acne hyperpigmentation; complications were burning/stinging/exfoliation; PIH occurred in 1 of 36 subjects.

A 2-MNG-containing depigmenting serum treats post-inflammatory hyperpigmentation in subjects of Fitzpatrick phototype IV-VI with acne-related PIH.

Acne = loss of C. acnes phylotype balance + dysbiosis, not hyperproliferation; antibiotics induce dysbiosis.

BP vehicle irritancy (surfactants/preservatives/alcohols); low-% formula without them well-tolerated.

Azelaic acid — 4 mechanisms (antimicrobial, tyrosinase inhibition, free-radical scavenging, reduced neutrophil ROS).

Azelaic acid also keratolytic.

Azelaic acid probably less effective than benzoyl peroxide on PGA (Cochrane RR 0.82).

Hidradenitis suppurativa >3x more prevalent in Black vs White; more severe, longer diagnostic delay.

Infant acid mantle is not yet established; still building toward adult pH over weeks-months.

pH regulates the enzymes holding the stratum corneum together; infant mantle is mid-construction.

True soap/high-pH cleansers vetoed for babies — infant acid mantle still forming, pH regulates the enzymes holding the stratum corneum together.

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.

Hard water dramatically increases barrier damage from surfactant cleansers — calcium/magnesium ions bind to surfactants and remain on skin after rinsing.

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.

Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.

Skin pH rises after a single wash and takes hours to recover; soap causes the greatest pH rise of any cleanser type tested.

Skin's optimal surface pH sits around 4.5-5.5; a single alkaline exposure measurably raises pH and recovery takes hours.

Ambient humidity and temperature strongly affect the stratum corneum; colder/drier regions show markedly higher population-level dry-skin burden than warm/humid ones.

Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface.

Skin's acidic pH supports barrier repair and antimicrobial defense; pH stays raised for hours after even a single wash.

Skin surface pH rises after a single wash, even water alone; recovery takes up to several hours.

In elderly dry skin, high TEWL tracks high pH, low hydration, low surface lipid.

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.

Triterpene constituents of shea butter's unsaponifiable fraction have anti-inflammatory activity.

Shea butter is a component of evidence-backed eczema barrier formulations.

Traditional wound-healing use of shea butter is documented.

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.

Panthenol (pro-vitamin B5) accelerates post-procedure skin barrier recovery, reduces transepidermal water loss, and improves stratum corneum moisture and barrier markers.

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.

Hard water dramatically increases barrier damage from surfactant cleansers — calcium/magnesium ions bind to surfactants and remain on skin after rinsing.

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.

Ambient humidity and temperature strongly affect the stratum corneum; colder/drier regions show markedly higher population-level dry-skin burden than warm/humid ones.

Humectants (urea, glycerol) increase stratum-corneum hydration; occlusives reduce water loss by sealing the surface.

Skin's acidic pH supports barrier repair and antimicrobial defense; pH stays raised for hours after even a single wash.

A fragrance-free barrier-repair cream with hyaluronic acid healed pedal fissures as effectively as urea 40% in a double-blind RCT (n=48), without the burning/irritation salicylic-acid formulas can cause.

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.

Skin's acidic pH supports barrier repair and antimicrobial defense; pH stays raised for hours after even a single wash.

Surfactants remove not just grease and dirt but also corneocytes, lipids, and proteins; repeated over-exposure causes irritant dermatitis.

Management of hand-hygiene-driven irritant contact dermatitis is choosing less-irritating products plus frequent moisturizer, not washing less.

Triterpene constituents of shea butter's unsaponifiable fraction have anti-inflammatory activity.

Shea butter is a component of evidence-backed eczema barrier formulations.

Traditional wound-healing use of shea butter is documented.

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.

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.

HOCl is produced endogenously by neutrophils as part of the innate immune response.

Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.

Eczema in skin of color shows greater extensor involvement, dyspigmentation, and papular/lichenified presentations; erythema is harder to appreciate, leading to underestimation of disease severity.

Eczema in skin of color may appear psoriasiform, lichenoid, scaly or papular with a violaceous color, with higher prevalence of PIH than White patients.

Higher prevalence, persistence, and severity of atopic dermatitis in skin-of-color populations; erythema assessment can underscore severity; greater risk of nodularity and hyper/hypopigmentation.

Black children are at roughly six times greater risk for severe atopic dermatitis than white children.

Pigmentary sequelae (hyper-, hypo-, depigmentation) are a distinct feature of atopic dermatitis in skin of color; xerosis is more visible in melanin-rich skin.

In psoriasis on skin of color, erythema is often less apparent, plaques may appear violaceous or dark brown; delayed diagnosis, greater biopsy reliance, reduced diagnostic accuracy; greater body-surface involvement, thicker scale; PIH can persist for years after resolution.

Plaque psoriasis prevalence is lower in people with skin of color but tends to be more severe; less likely to receive biologic treatment; worse quality-of-life impact.

Black skin shows increased transepidermal water loss, decreased ceramide levels, and lower stratum corneum pH; management emphasizes low-pH products and emollients.

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.

L-ascorbic acid is the most-studied vitamin C form (direct tyrosinase inhibition); requires pH 2.5-3.5 to penetrate, which can itself trigger PIH on reactive Fitzpatrick IV-VI skin.

Fitzpatrick VI skin has a natural SPF equivalent of approximately 13.

Topical retinoids increase collagen and normalize keratinocytes/melanocytes, improving wrinkles, texture, and tone.

Thicker/more compact dermis on skin of color makes facial lines less noticeable; higher epidermal melanin makes darker skin more vulnerable to dyspigmentation with age.

Photoaging from cumulative UV exposure is the greatest contributing factor to visible facial aging.

Topical retinoids build collagen; on skin of color the gentlest effective strength avoids irritation-triggered PIH.

The Fitzpatrick scale (developed 1975 by Thomas Fitzpatrick) classifies UV response, not appearance; Types I-VI run from always-burns/never-tans to never-burns/tans-deeply; higher melanin density means higher PIH risk, not more protection; product concentrations formulated/tested on Fitzpatrick I-III can inflame IV-VI skin.

Curl arises from asymmetric cell differentiation in the hair root, producing an elliptical cortex; mechanism structurally the same across ethnic origin, more pronounced in coily hair.

African/African-diaspora scalp hair is significantly more curled on average than European or East Asian hair.

Coily/African-type hair shows lower water sorption and distinct cuticle lipid structure vs straighter hair; fragility best attributed to knotting/crack formation rather than cross-sectional shape alone.

Coconut oil (unlike mineral or sunflower oil) penetrates the hair shaft, measurably reduces protein loss from grooming, correlates with lower Hair Breakage Index.

L-ascorbic acid is the most-studied vitamin C form (direct tyrosinase inhibition); requires pH 2.5-3.5 to penetrate, which can itself trigger PIH on reactive Fitzpatrick IV-VI skin.

Oral tranexamic acid 250mg twice daily for 3 months produced a 49% mMASI reduction vs 18% placebo.

Tranexamic acid is an antifibrinolytic lysine analogue that binds the lysine-binding sites of plasminogen and so reduces plasmin generation. In guinea pigs, topical tranexamic acid applied after UV exposure reduced UV-induced pigmentation and arachidonic-acid-induced pigmentation; the authors propose that UV raises epidermal plasmin activity, plasmin promotes arachidonic acid release and prostaglandin production, and these arachidonic-acid metabolites stimulate melanocyte tyrosinase (arachidonic-acid metabolites do stimulate tyrosinase in cultured human melanocytes). This chain rests on animal and cell-culture data and is not established in humans.

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.

2-5% niacinamide produced statistically significant melanin-density reduction over 4-8 weeks (35-68% melanosome-transfer inhibition in coculture).

The core PIH mechanism (melanocytes overproduce pigment in response to inflammation on elevated-melanin-density skin).

Chronic friction induces hyperpigmentation (frictional melanosis).

PIH is often chronic; improves only partially and slowly.

Iron-oxide sunscreen protects against visible-light-induced pigmentation in Fitzpatrick III-VI, including melasma, where SPF alone did not.

Visible light is ~45% of solar spectrum and can induce persistent darkening, especially in skin of color.

Tranexamic acid produced significantly greater melasma improvement (MASI) than ascorbic acid mesotherapy in skin-of-color patients.

Azelaic acid inhibits tyrosinase and accelerates keratinocyte turnover.

Niacinamide at 10-12% blocks melanosome transfer.

Visible light induces pigmentation in darker skin; iron-oxide tints block it, plain nanoparticle mineral filters do not.

Iron-oxide/tinted photoprotection corroboration for skin of color.

Physical sunscreens with iron oxide and silicones give a photoprotective + camouflage effect in melasma.

Visible light's role in melasma is established; its role in PIH specifically remains to be demonstrated.

L-ascorbic acid penetrates skin only below pH 3.5, optimal absorption ~20%; several derivatives did not raise skin vitamin C levels in the same study.

PIH affects darker skin with greater frequency/severity; azelaic acid, niacinamide, ascorbic acid are recognized topical depigmenting agents in skin of color.

Citrus-induced phytophotodermatitis can present as hyperpigmentation without preceding inflammation, especially in dark-skinned people.

On skin of color, irritation itself can trigger PIH; clinical approach is to start low and titrate up.

Topical retinoids reduce hyperpigmentation in patients with skin of color and should be started early.

All-Black-patient RCT: 0.1% tretinoin improved melasma (MASI) 32% vs 10% vehicle over 40 weeks; side effects limited to mild retinoid dermatitis in 67%.

Frictional melanosis is an acquired pigmentary disorder — brown pigmentation from repeated rubbing — recognized among frictional dermatoses, prevalent in more pigmented skin.

In richly pigmented skin, frictional/postinflammatory pigmentation is common; PIH risk requires cautious, individualized treatment.

The Fitzpatrick scale (developed 1975 by Thomas Fitzpatrick) classifies UV response, not appearance; Types I-VI run from always-burns/never-tans to never-burns/tans-deeply; higher melanin density means higher PIH risk, not more protection; product concentrations formulated/tested on Fitzpatrick I-III can inflame IV-VI skin.

Chronic friction induces hyperpigmentation (frictional melanosis).

Occlusion and hydration increase how deeply/quickly topical actives penetrate skin.

Pregnancy-related hyperpigmentation is common and usually eases postpartum.

PIH is often chronic; improves only partially and slowly.

Hypo-oestrogenism lowers water retention and impairs barrier function, raising irritant-dermatitis risk.

General management of vulvar dermatoses is gentle cleansing, avoidance of irritants, optimized skincare, patch testing where contact allergy is suspected.

Lichen simplex chronicus produces hyperpigmented lichenified plaques from rubbing; PIH/hypopigmentation varies with natural skin color.

Few studies focus on vulvar disease in skin of color; lichen sclerosus, vitiligo, and inflammatory vulvitis are frequently misdiagnosed as one another; mean delay to LS diagnosis 16.43 months.

Lichen sclerosus is often misdiagnosed as vitiligo on darker skin due to hypopigmentation contrast; scarring and thickening are the distinguishing signs vitiligo does not produce.

Visible light induces pigmentation in darker skin; iron-oxide tints block it, plain nanoparticle mineral filters do not.

Iron-oxide/tinted photoprotection corroboration for skin of color.

Physical sunscreens with iron oxide and silicones give a photoprotective + camouflage effect in melasma.

Visible light's role in melasma is established; its role in PIH specifically remains to be demonstrated.

L-ascorbic acid is the most-studied vitamin C form (direct tyrosinase inhibition); requires pH 2.5-3.5 to penetrate, which can itself trigger PIH on reactive Fitzpatrick IV-VI skin.

Tranexamic acid is an antifibrinolytic lysine analogue that binds the lysine-binding sites of plasminogen and so reduces plasmin generation. In guinea pigs, topical tranexamic acid applied after UV exposure reduced UV-induced pigmentation and arachidonic-acid-induced pigmentation; the authors propose that UV raises epidermal plasmin activity, plasmin promotes arachidonic acid release and prostaglandin production, and these arachidonic-acid metabolites stimulate melanocyte tyrosinase (arachidonic-acid metabolites do stimulate tyrosinase in cultured human melanocytes). This chain rests on animal and cell-culture data and is not established in humans.

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.

HOCl is produced endogenously by neutrophils as part of the innate immune response.

Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.

A brief benzoyl peroxide contact suppresses S. aureus without the full-spectrum damage of longer-contact antibacterial washes.

Acne is a common cause of PIH, particularly in skin of color; resulting marks are often more distressing to patients than the acne itself.

In skin of color, acne treatment must balance efficacy against irritation, because irritation itself triggers PIH; treat early, titrate gently.

Topical retinoids and azelaic acid treat acne and reduce post-acne hyperpigmentation in skin of color.

Nd:YAG laser is safe and effective for PFB on Fitzpatrick IV-VI skin; other wavelengths risk burns or paradoxical pigmentation.

With-the-grain shaving and single-blade/foil razors are the standard mechanism-based recommendation for PFB; direct comparative clinical evidence is limited and partly mixed — a consistent regimen with pre/post-shave care may matter as much as blade count.

Keloid formation is significantly more prevalent in Fitzpatrick IV-VI populations.

HOCl is produced endogenously by neutrophils as part of the innate immune response.

Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.

Erythema-based severity scales are validated on Fitzpatrick I-III; skin-of-color patients are systematically underdiagnosed or misclassified by tools not designed for their presentations.

The core PIH mechanism (melanocytes overproduce pigment in response to inflammation on elevated-melanin-density skin).

Hard water dramatically increases barrier damage from surfactant cleansers — calcium/magnesium ions bind to surfactants and remain on skin after rinsing.

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.

Iron-oxide sunscreen protects against visible-light-induced pigmentation in Fitzpatrick III-VI, including melasma, where SPF alone did not.

Visible light is ~45% of solar spectrum and can induce persistent darkening, especially in skin of color.

Fitzpatrick VI skin has a natural SPF equivalent of approximately 13.

The FDA approved bemotrizinol (Tinosorb S) as a sunscreen active on June 9, 2026, effective August 9, 2026 — the first new UV filter approved for US use in 20 years.

Waterproof,' 'sunblock,' and 'sweatproof' are prohibited on US sunscreen labels; only 'water resistant 40/80 minutes' is permitted.

HOCl is produced endogenously by neutrophils as part of the innate immune response.

Sodium hypochlorite solution pH is 11-12; disrupts skin acid mantle on contact.

Antiperspirant/deodorant products can compromise the axillary microbiome balance.

Essential oils marketed as natural (lavender, tea tree) are a documented cause of allergic contact dermatitis.

A brief benzoyl peroxide contact suppresses S. aureus without the full-spectrum damage of longer-contact antibacterial washes.

One small study found no aluminum detected in apocrine glands after antiperspirant use; concluded absorption-risk concerns look unfounded on that data.

Essential oils (lavender, tea tree) are a documented cause of allergic contact dermatitis.

Intertrigo is a superficial inflammatory condition of skin folds triggered by friction/moisture/heat/poor ventilation; can become secondarily infected (often Candida).

Frictional melanosis is an acquired pigmentary disorder — brown pigmentation from repeated rubbing — recognized among frictional dermatoses, prevalent in more pigmented skin.

In richly pigmented skin, frictional/postinflammatory pigmentation is common; PIH risk requires cautious, individualized treatment.