Platelet-rich fibrin
BioChemEntityPlatelet‑rich fibrin is an autologous fibrin matrix that traps platelets, leukocytes, and growth factors, releasing them slowly over 7–14 days for longer activity than PRP.
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Platelet-Rich Plasma
BioChemEntityA concentrated blood-derived preparation containing 3-5 times normal platelet levels, rich in growth factors that signal tissue repair and collagen synthesis.
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Platelet-rich plasma therapy
MedicalTherapyRegenerative treatment using your concentrated blood plasma to stimulate natural collagen production and tissue repair in facial skin or thinning hair areas.
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Poly-gamma-glutamic acid
MolecularEntityPoly-gamma-glutamic acid (PGA) is a naturally occurring anionic polypeptide. Its polyanionic structure gives it physical and biological properties that distinguish it from standard humectants.
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Poly-L-Lactic Acid
MedicalTherapyA biodegradable synthetic polymer injected as microspheres to stimulate gradual collagen neogenesis via a controlled foreign body response and direct fibroblast PI3K/AKT activation.
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Polydeoxyribonucleotide
MedicalTherapyPDRN is a DNA-derived biopolymer prepared from salmon or trout sperm cells, specifically referring to the shorter-chain fragment preparations in the 50–1,500 kDa molecular weight range.
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Polynucleotides
MedicalTherapyDNA-derived injectable treatment that stimulates tissue regeneration whilst calming inflammation, particularly beneficial for reactive or sensitised skin.
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Polyunsaturated fatty acids
ChemicalSubstanceA class of dietary fats defined by multiple double bonds in their carbon chain. Includes the omega-3 and omega-6 families.
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Postprandial glucose response
BiologicalProcessThe acute glucose and insulin trajectory following a meal, its amplitude, timing, and descent, determining both the immediate neurological environment and glycation accumulation.
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Pro‑opiomelanocortin
ProteinA single polypeptide precursor that, depending on which tissue processes it, yields entirely different biological outcomes: appetite suppression, cortisol production, photoprotective pigmentation.
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Proline
ChemicalSubstanceAn amino acid that forms the structural backbone of the collagen triple helix, where it provides rigidity and resistance to mechanical stress.
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Protease-activated receptor 2
ProteinA protease‑activated GPCR that guides normal barrier repair under controlled activation but amplifies inflammation, itch, and Th2 signalling when protease activity is dysregulated.
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Psoriasis
MedicalConditionA T-cell-mediated autoimmune skin disease driven by the IL-23/Th17 axis, producing keratinocyte hyperproliferation and systemic inflammatory burden extending to joints and cardiovascular tissue.
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Psychological stress
MedicalConditionPsychological stress produces measurable, mechanistically defined changes in skin biology, including accelerated collagen degradation, DNA damage, and inflammageing.
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Pyrrolidone carboxylic acid
ChemicalSubstanceA naturally occurring humectant produced in the stratum corneum from filaggrin-derived glutamine. One of the largest single components of natural moisturising factor (NMF) by volume.
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Pyruvate dehydrogenase complex
ProteinThe mitochondrial enzyme that converts pyruvate to acetyl‑CoA and is inhibited by PDK‑mediated phosphorylation, gating glucose entry into oxidative metabolism.
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Radiofrequency Microneedling
MedicalTherapyA minimally invasive treatment combining fine needle micro-injury with bipolar radiofrequency energy delivered precisely at needle tips into the dermis.
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Randle cycle
BiologicalProcessThe Randle Cycle describes the reciprocal competition between glucose and fatty acids as cellular fuel sources; when one is being oxidised, it suppresses the other.
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Rapid weight loss
BiologicalProcessRapid weight loss, typically defined as loss exceeding 1–1.5kg per week, or greater than 1% of body weight per week sustained over multiple weeks
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Reactive oxygen and nitrogen species
ChemicalSubstanceA family of chemically reactive molecules comprising reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated continuously in skin tissue.
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Reticular dermis
AnatomicalStructureThe deeper, thicker layer of the dermis, composed of dense Type I collagen bundles, thick elastic fibres, and ground substance.
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Retinoid
ChemicalSubstanceVitamin A derivatives that act via retinoic acid receptors but differ in receptor selectivity, conversion steps, and tolerability, making clinical choice dependent on skin state and treatment goals.
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Rosacea
MedicalConditionA chronic inflammatory condition driven by a self-amplifying KLK5/LL-37 feedback loop, neurovascular sensitisation, and barrier dysfunction — not simply reactive or vascular skin.
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Sapienic acid
MolecularEntityA C16:1 delta-6 monounsaturated fatty acid produced exclusively by human sebaceous glands. The most abundant fatty acid in human sebum.
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Saturated fatty acids
ChemicalSubstanceA class of fatty acids characterised by a fully saturated carbon chain with no double bonds, making them chemically stable and resistant to oxidation.
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Scalp
AnatomicalStructureDistinct tissue where hair follicles reside, with different characteristics than facial skin requiring adjusted treatment approaches.
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Sebaceous gland
AnatomicalStructureHolocrine secretory glands distributed across most body skin, embedded in the dermis and typically connected to a hair follicle as part of the pilosebaceous unit.
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Sebaleic acid
MolecularEntityA C18:2 delta-5,8 polyunsaturated fatty acid produced exclusively in human sebaceous glands by elongation and desaturation of sapienic acid.
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Sebocyte
AnatomicalStructureThe lipid-producing cells of the sebaceous gland, responsible for synthesising and secreting the components of sebum.
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Sebum
ChemicalSubstanceThe complex lipid mixture secreted by sebaceous glands onto the skin surface via the follicular canal.