Edible Fungi and Skin Redox Homeostasis: Bioactive Diversity, Processing, Oral Exposure, and Evidence Gaps

Oxidative stress drives skin aging, barrier impairment, and inflammatory amplification, making dietary antioxidants potential systemic contributors to cutaneous redox homeostasis. Edible fungi are distinctive sources of redox-active metabolites, particularly ergothioneine, a stable sulfur-containing antioxidant whose cellular uptake is mediated by the ergothioneine transporter OCTN1 (SLC22A4). This review evaluates ergothioneine, polysaccharides and β-glucans, cordycepin, phenolics, and Ganoderma triterpenoids as processing-sensitive dietary bioactives with redox relevance rather than topical cosmetic ingredients. We examine how cultivation, drying, cooking, extraction, fermentation, and microbial biomanufacturing determine antioxidant formation, retention, oral bioaccessibility, and dose realism, and how antioxidant response, inflammatory, mitochondrial, and gut microbiota-mediated pathways connect intake to skin endpoints. The strongest oral evidence concerns biomarker-linked ergothioneine-rich Pleurotus. Smaller Flammulina velutipes and Sparassis crispa trials report hydration or transepidermal water loss signals without comparable exposure biomarkers, whereas purified ergothioneine provides provisional non-mushroom food evidence. Compared with better-established oral ingredients, edible fungi offer distinctive food technology advantages but a narrower human evidence base. Priorities include processing-aware quality and safety markers, contaminant control, standardized digestion models, dose-realistic exposure estimates, and biomarker-anchored randomized human trials.