Pigment Vocabulary — A Cheatsheet for Melasma, PIH, and Tone Evenness

A working glossary of the terms that come up when people learn about pigment biology, melasma, post-inflammatory hyperpigmentation, and the science behind CODE3's formula. Definitions are written for non-specialists with the precision a physician would expect. Where a peer-reviewed source supports the term's relevance to CODE3, a PubMed citation is linked.

Pigment biology and mechanism

The cellular and signaling vocabulary that explains how pigment is made — and why CODE3's mechanism story is "upstream of melanin production," not "melanin suppression."

Melanin

The pigment molecule responsible for skin, hair, and eye color. Produced by specialized cells called melanocytes. Melanin is protective — it absorbs UV radiation and limits photodamage. The clinical goal in pigment care is to correct abnormal pigment patterns, not to suppress melanin generally.

Eumelanin(brown-black melanin)

The brown-to-black form of melanin, dominant in darker skin types and providing the strongest UV protection.

Pheomelanin(red-yellow melanin)

The red-to-yellow form of melanin, more common in lighter skin and red hair. Provides less UV protection than eumelanin.

Melanocyte

The pigment-producing cell in the basal layer of the epidermis. Each melanocyte distributes melanin to roughly 30–40 surrounding keratinocytes via cellular projections called dendrites. Melanocyte activity (not number) is what changes with most pigment disorders.

Melanosome

The intracellular organelle inside melanocytes where melanin is synthesized and packaged for transfer to surrounding skin cells.

Melanogenesis

The biochemical process of melanin production. Begins with the amino acid tyrosine, catalyzed by the enzyme tyrosinase, and proceeds through several intermediates to either eumelanin or pheomelanin.

Tyrosinase

The rate-limiting enzyme in melanin synthesis. It converts the amino acid tyrosine into the precursor DOPA, which then becomes melanin. Hydroquinone and several other classical pigment-correcting agents work by inhibiting tyrosinase. CODE3's hero active tranexamic acid does not work this way — TXA acts upstream of tyrosinase, on signaling pathways that activate melanocytes in the first place.

Plasmin

A serine protease enzyme produced from plasminogen. Plasmin signaling has been implicated in melanocyte activation, including pathways related to alpha-MSH. Tranexamic acid is studied for inhibiting the activation of plasminogen into plasmin, which is the proposed mechanism for its melasma effect.

Plasminogen

The inactive precursor protein that, when activated, becomes plasmin. Tranexamic acid is studied for blocking the activation of plasminogen on cell surfaces, including keratinocytes adjacent to melanocytes.

Tissue plasminogen activator(tPA)

An enzyme that converts plasminogen into plasmin. Implicated in the upstream pigment signaling cascade that tranexamic acid is studied to interrupt.

Alpha-melanocyte-stimulating hormone(alpha-MSH, α-MSH)

A peptide hormone derived from proopiomelanocortin (POMC) that activates melanocytes via the MC1R receptor, increasing melanin production. UV exposure and inflammation can both increase alpha-MSH signaling, which is one reason inflammation drives pigment.

Proopiomelanocortin(POMC)

A precursor protein in keratinocytes and the pituitary gland that, when cleaved, produces alpha-MSH and other peptides. Skin POMC expression is increased by UV exposure.

MC1R(melanocortin 1 receptor)

The melanocyte cell-surface receptor for alpha-MSH. MC1R activation increases eumelanin production. Genetic variation in MC1R explains much of the difference between red hair / fair skin and darker phototypes.

MITF(Microphthalmia-associated transcription factor)

The master transcription factor regulating melanocyte development and melanin production. MITF activity is downstream of MC1R signaling.

Stem cell factor(SCF, KIT ligand)

A signaling protein produced by keratinocytes that stimulates melanocyte proliferation and pigment production. Elevated in lesional melasma skin compared to surrounding normal skin.

Endothelin-1

A signaling peptide produced by keratinocytes that increases melanocyte activity. One of the inflammatory-pathway intermediaries that links skin inflammation to pigment.

Reactive oxygen species(ROS, oxidative stress)

Highly reactive oxygen-containing molecules generated by UV exposure, inflammation, and normal cellular metabolism. ROS contribute to melanocyte activation and abnormal pigment formation. Quercetin, a hero active in CODE3, is a flavonoid antioxidant included specifically to address oxidative-stress signaling in pigment pathways.

Inflammatory pigment cascade

The chain of cellular events linking skin inflammation (from acne, eczema, sun damage, allergic reactions) to increased melanocyte activity and pigment deposition. Bakuchiol, a hero active in CODE3, is included to support a calmer inflammatory environment that doesn't perpetuate this cascade.

Conditions and diagnoses

The pigment conditions most often discussed in dermatology consultations and patient communities. Diagnoses should always be confirmed by a board-certified dermatologist.

Melasma(also called chloasma when associated with pregnancy)

A common acquired pigment disorder characterized by symmetric brown-to-grayish patches, most often on the cheeks, forehead, upper lip, and chin. More common in women than men and in darker phototypes. Hormonal shifts, sun exposure, and inflammation are the leading triggers.

Post-inflammatory hyperpigmentation(PIH)

Pigment patches that develop after a skin injury or inflammatory event — acne, eczema, irritation, contact dermatitis, picking, friction, or burns. PIH is more common and more persistent in skin of color (Fitzpatrick III–VI). Distinct from post-inflammatory erythema (PIE), which is the redness that often precedes PIH.

Post-inflammatory erythema(PIE)

Persistent redness following inflammation, common in lighter phototypes after acne. Distinguished from PIH (which is brown-pigment) by appearing red-pink and being a vascular rather than melanin-based phenomenon.

Solar lentigo(solar lentigines, age spots, liver spots, sun spots)

Discrete brown macules that develop on chronically sun-exposed skin. Distinct from melasma (which is patchy and often symmetric) and from freckles (which fade with sun avoidance). Solar lentigines are typically more sharply demarcated and persist year-round.

Ephelides(freckles)

Small light-brown macules that darken with sun exposure and fade in winter. Genetically determined; common in lighter phototypes with red or blond hair.

Hyperpigmentation

The general category of skin conditions where melanin is increased relative to surrounding skin. Includes melasma, PIH, solar lentigines, ephelides, and several less common entities.

Hypopigmentation

The opposite of hyperpigmentation — areas of skin with reduced melanin. Includes vitiligo, post-inflammatory hypopigmentation, and tinea versicolor.

Dyschromia

A general term for any color change in skin — covers both hyperpigmentation and hypopigmentation, plus blue, gray, and other discolorations. Used in dermatologic literature when the specific diagnosis is uncertain.

Vitiligo

An autoimmune condition in which melanocytes are destroyed, producing well-demarcated white patches. Distinct from the abnormal-pigment focus of CODE3, which addresses excess melanin patterns rather than melanocyte loss.

Ochronosis(exogenous ochronosis)

A paradoxical blue-black pigmentation that can develop after long-term hydroquinone use, particularly in skin of color. One of the documented adverse effects driving interest in non-hydroquinone pigment-correction approaches.

Periorbital hyperpigmentation(under-eye dark circles)

Pigment darkening around the eyes. Multiple causes including dermal melanosis, vascular shadowing, structural shadows, and chronic eczema. Often confused with simple under-eye hollows.

Hori's nevus(acquired bilateral nevus of Ota-like macules, ABNOM)

A dermal pigmentation disorder presenting as bilateral blue-gray patches on the cheeks and temples, most common in East Asian patients. Sometimes mistaken for melasma but pigment is deeper and treatment differs.

Acanthosis nigricans

Velvety dark patches in body folds (neck, armpits, groin). Often associated with insulin resistance or other endocrine conditions. Pigment-correcting topicals address the discoloration but not the underlying condition.

Café-au-lait macules

Light-brown patches present from birth or early childhood. Multiple café-au-lait macules can be associated with neurofibromatosis type 1 and warrant pediatric evaluation.

Riehl's melanosis

A pigmented contact dermatitis presenting as brown-gray patches, often on the face and neck. Frequently triggered by fragrance or other contact allergens in cosmetics.

Severity and measurement

How dermatologists quantify pigment severity in clinical practice and trials.

MASI score(Melasma Area and Severity Index)

The standard scoring system for melasma severity. Combines area of involvement, darkness, and homogeneity across four facial regions (forehead, right malar, left malar, chin). Higher scores indicate more severe melasma. MASI score change is the primary endpoint in many topical melasma trials.

mMASI(modified MASI)

A simplified version of MASI that drops the homogeneity component, improving inter-rater reliability. Now the more common scoring system in published melasma trials.

Fitzpatrick phototype(Fitzpatrick skin type, FST I–VI)

A six-point classification of skin type based on response to UV exposure (sunburn vs. tanning tendency). FST I burns easily and tans poorly; FST VI rarely burns and pigments deeply. Pigment conditions like PIH are more common and more persistent in FST IV–VI.

Individual Typology Angle(ITA)

A continuous, instrument-measured skin tone classification based on L* and b* values from colorimetry. More precise than Fitzpatrick phototype for research because it produces a numeric value rather than a categorical bucket.

Colorimetry(chromameter, spectrophotometry)

Instrumental measurement of skin color, typically reported in the L* a* b* color space. Used in clinical trials to objectively quantify pigment changes that the human eye might miss.

L* a* b* color space(CIELAB)

The standard color-measurement system in dermatology. L* measures lightness (0 black, 100 white), a* measures red-green axis, b* measures yellow-blue axis. Pigment improvement typically shows as increased L* and decreased b*.

VISIA imaging

A standardized facial-photography system used in dermatology offices to track pigment, redness, pores, and other skin features over time. Useful for documenting treatment response.

Wood's lamp

A handheld UV-A lamp used in dermatology to distinguish epidermal from dermal pigment. Epidermal melasma appears more enhanced under Wood's light; dermal melasma appears less enhanced. Mixed-type melasma shows both patterns.

Triggers and causes

The environmental, hormonal, and behavioral factors that drive abnormal pigment.

UV radiation(UVA, UVB)

The single most important environmental driver of melasma and most pigment disorders. UVA penetrates deeper and is implicated in long-term pigment dysregulation; UVB causes more acute damage. Daily broad-spectrum sunscreen is the foundation of any pigment-correction regimen.

Visible light pigmentation(blue light, HEV)

Visible light, especially the high-energy blue end of the spectrum, has been shown to induce pigmentation in darker phototypes even when UV is fully blocked. Tinted sunscreens with iron oxide pigments are the current standard for blocking visible light.

Hormonal melasma

Melasma triggered by hormonal shifts including pregnancy, oral contraceptives, hormone replacement therapy, and conditions like polycystic ovary syndrome (PCOS). Estrogen and progesterone receptors on melanocytes are part of the proposed mechanism.

Heat-induced melasma(thermal melasma)

Pigment exacerbated by heat exposure (saunas, hot yoga, cooking, hot climates) independent of UV. Heat triggers inflammatory cascades that can drive melasma flares.

Drug-induced pigmentation

Pigment patterns triggered or worsened by medications, including some antibiotics (minocycline), antimalarials, amiodarone, and certain antiepileptics. Discontinuing the offending drug is typically the first step.

Friction-induced pigmentation

Pigment on areas of chronic friction — neck, ankles, intertriginous areas. A specific subtype, frictional dermal melanosis, presents in skin of color from clothing or scrubbing.

Pigment-correcting actives

The most relevant ingredients in topical pigment care, with mechanism descriptions and (where applicable) the CODE3 citation.

Tranexamic acid(TXA, trans-4-aminomethylcyclohexanecarboxylic acid)

A synthetic lysine analog that inhibits the activation of plasminogen to plasmin. Originally developed and FDA-approved as a systemic antifibrinolytic for bleeding; the topical melasma application is more recent and is supported by head-to-head RCTs against hydroquinone with comparable efficacy and similar or better tolerability. CODE3 features 10% topical TXA as a hero active.

Citations: PMID 38918942, PMID 31057273.

Hydroquinone

A tyrosinase inhibitor and the historical standard topical pigment-correcting agent. Effective for melasma and PIH but associated with adverse effects including ochronosis (paradoxical blue-black pigmentation), rebound pigmentation, and contact sensitization with prolonged use. In the U.S., over-the-counter hydroquinone was removed in 2020 and is now prescription-only.

Bakuchiol

A meroterpene phenol from Psoralea corylifolia. Marketed and studied as a retinol-tolerability alternative; head-to-head RCTs vs. retinol show non-inferior photoaging outcomes with significantly less scaling, stinging, and irritation. CODE3 includes bakuchiol as a hero active for the inflammatory-environment story relevant to pigment management.

Citation: PMID 29947134.

Quercetin

A flavonoid antioxidant found in many plant foods. In topical formulations, quercetin is included for its oxidative-stress modulation in pigment signaling. CODE3 includes quercetin as a hero active for the oxidative-stress mechanism, not as a standalone bleaching agent.

Citation: PMID 40177799.

Niacinamide(vitamin B3)

A water-soluble vitamin with multiple skin-relevant mechanisms. Studied head-to-head against hydroquinone for melasma with similar objective colorimetry improvement and fewer side effects. A foundation active in CODE3.

Citation: PMID 21822427.

Retinol(retinoid family)

A vitamin-A derivative that increases skin cell turnover and modulates pigment over weeks of use. Effective but commonly associated with irritation, scaling, and stinging. Not used during pregnancy. Distinct from bakuchiol, which is sometimes used as a retinol-tolerability alternative.

Vitamin C(L-ascorbic acid)

A classic topical antioxidant with mild tyrosinase-inhibition properties. Effective in stable formulations; instability is the main practical limitation.

Kojic acid

A natural tyrosinase inhibitor produced by certain fungi. Used in some over-the-counter brightening serums.

Azelaic acid

A dicarboxylic acid with mild tyrosinase inhibition and anti-inflammatory properties. Used both for acne and pigment indications. Available OTC in lower concentrations and by prescription at 15–20%.

Cysteamine

A potent topical pigment-correcting agent that works on a different pathway than tyrosinase inhibition. Effective but historically limited by an unpleasant sulfur odor; newer formulations have improved tolerability.

Arbutin

A naturally occurring glycosylated form of hydroquinone (alpha-arbutin or beta-arbutin). Milder than hydroquinone but with related mechanism.

Glycolic acid

An alpha hydroxy acid (AHA) used for exfoliation and surface pigment improvement. Often combined with other pigment-correcting actives.

Mandelic acid

A larger alpha hydroxy acid often preferred for pigment-prone or sensitive skin because of its slower penetration and gentler tolerability profile.

Procedures (clinical context)

In-office procedures sometimes used for pigment management. CODE3 is a topical formula used in routine skincare; for procedure-specific protocols and post-procedure care, follow your dermatologist's or plastic surgeon's instructions.

Chemical peel

An in-office treatment using glycolic, salicylic, lactic, mandelic, or trichloroacetic acid to exfoliate at controlled depth. Used adjunctively for pigment, often as part of a longer regimen.

Microneedling

A procedure using fine needles to create controlled micro-injuries that stimulate collagen and improve topical absorption. Used for pigment, scars, and texture.

Q-switched laser

A nanosecond-pulse laser that targets pigment particles. Used for solar lentigines, dermal pigment, and tattoo removal. Use in melasma is controversial because of the risk of paradoxical worsening.

Intense pulsed light(IPL)

A broad-spectrum light source used for solar lentigines, broken capillaries, and certain pigment patterns. Generally avoided in active melasma due to risk of rebound pigment.

Picosecond laser

A newer-generation laser using picosecond pulses to target pigment with less surrounding thermal damage than Q-switched. Used for tattoo removal and some pigment indications.

Skincare science and regulatory

Terms that come up in label reading, ingredient research, and FDA regulatory context.

Cosmetic OTC

A category of products regulated by the U.S. FDA as cosmetics rather than drugs. Cosmetic OTCs improve appearance, texture, or sensorial experience without making medical claims. CODE3 is regulated as a cosmetic OTC product.

FDA monograph

An FDA document specifying what active ingredients can be used in OTC drug categories (sunscreen, acne, antiperspirant). Hydroquinone was removed from OTC monograph status in 2020.

Patent-pending

A status indicating that a patent application has been filed but not yet granted. CODE3's TXA + bakuchiol + quercetin combination is patent-pending.

PubMed

A free database of biomedical literature maintained by the U.S. National Library of Medicine. Each indexed article has a unique PMID. Citations on the CODE3 evidence page link directly to PubMed.

PMID(PubMed identifier)

A unique numeric identifier assigned to each article indexed in PubMed. The format used to cite peer-reviewed dermatology evidence in CODE3 brand content.

DOI(Digital Object Identifier)

A persistent identifier for a digital document, typically a journal article. Used alongside PMIDs to link to the publisher's version of an article.

Randomized controlled trial(RCT)

A trial design in which participants are randomly assigned to treatment or control groups. The standard design for clinical efficacy evidence in dermatology and beyond.

Split-face trial

A trial design in which two treatments are applied to opposite halves of the same patient's face. Reduces between-patient variability and is useful for direct topical comparisons.

Penetration enhancer

An ingredient that improves the absorption of topical actives through the stratum corneum. Urea, included in CODE3, is one of the most studied penetration enhancers in topical dermatology.

Stratum corneum

The outermost layer of the epidermis, composed of corneocytes and lipids. The primary barrier topical actives must cross to reach living skin layers.

Epidermis

The outer layer of the skin, including the basal layer where melanocytes live. Most topical pigment correction targets epidermal pigment.

Dermis

The thicker layer beneath the epidermis containing collagen, elastin, blood vessels, and nerves. Dermal pigment (in mixed melasma, Hori's nevus, etc.) is harder to address topically because actives reach this depth less efficiently.

Broad-spectrum sunscreen

A sunscreen that protects against both UVA and UVB. Daily broad-spectrum SPF 30+ is the foundation of any pigment-correction regimen; topical actives like CODE3 work alongside, not instead of, daily UV protection.