Hair follicle
AnatomicalStructureComplex miniature organs embedded in the dermis and subcutis that cycle through growth (anagen), transition (catagen), and rest (telogen) phases throughout life.
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12 entities found starting with H Clear filters
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Hair loss
MedicalConditionUmbrella term for conditions causing increased hair shedding or thinning, ranging from temporary telogen effluvium to progressive androgenetic alopecia.
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Hallmarks of ageing
BiologicalProcessA framework of twelve interconnected biological processes - organised into Primary, Antagonistic, and Integrative tiers - that collectively produce the structural decline of ageing tissue.
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Hard water
ChemicalSubstanceWater with elevated dissolved calcium and magnesium content. Disrupts skin barrier function through four mechanistically independent pathways.
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Headache
MedicalSignOrSymptomNon-GI side effect of tirzepatide showing significant variation by injection site, with thigh injection reducing incidence by nearly half.
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Heparan sulfate proteoglycans
BioChemEntityGlycosaminoglycan-bearing proteins distributed across the dermal ECM and basement membrane that store and regulate growth factors including FGF2, FGF7, FGF10, and VEGF in a protected on-site depot.
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High sugar and processed food intake
BiologicalProcessDietary pattern of elevated sugar and processed food intake that leads to increased blood glucose and potential skin effects.
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Histidine
ChemicalSubstanceAn essential amino acid with a uniquely skin-specific metabolic pathway. Filaggrin is particularly rich in histidine, and its degradation converts histidine to trans-urocanic acid.
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Hyaluronic acid
ChemicalSubstanceA glycosaminoglycan that forms the water-retaining ground substance of the dermis and maintains the mechanical environment fibroblasts need for collagen synthesis.
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Hyaluronic acid lip fillers
MedicalTherapyHyaluronic acid lip fillers are injectable cross-linked HA gels used to augment lip volume, define the vermilion border, and restore lip proportion lost through ageing or asymmetry.
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Hyperpigmentation
MedicalConditionHyperpigmentation describes the localised or diffuse overproduction or abnormal distribution of melanin in the skin. It is not a single condition but three mechanistically distinct presentations.
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Hypothalamic–pituitary–adrenal axis
BiologicalProcessThe body’s central stress‑response system, driving CRH→ACTH→cortisol signalling systemically and via a parallel cutaneous HPA axis that regulates skin immunity, barrier function, and repair.