Dermatological Evidence for Coumarins Occurring in Apiaceae: Separating Traditional Use, Botanical Occurrence, and Compound Pharmacology

Apiaceae plants have documented uses for pruritic and inflammatory skin conditions. Their coumarins include clinical photosensitizers and experimental candidates, but botanical occurrence alone does not establish equivalence to traditional preparations. To assess dermatological evidence for Apiaceae coumarins and identify where traditional use, tested material, skin exposure, and photosafety support further development, this narrative review drew on PubMed and PubMed Central records, targeted web searches, citation checking, guidelines, and regulatory sources; documented search and update activities took place in July and September 2026. Studies were compared by disease, material, route, comparator, skin exposure, and photosafety. Controlled psoralen–ultraviolet A (UVA) treatment has established clinical use. An authenticated Cnidium monnieri fruit extract and its isolated osthol provide a material-specific experimental link. Osthol reduced dermatitis and scratching in mouse models. Imperatorin reduced psoriasiform changes after systemic dosing and rosacea-like inflammation after topical application in mice. Umbelliferone slightly altered pigmentation measures in 12 healthy volunteers and improved oral-dose wound closure in diabetic mice. Comparative topical efficacy at measured skin concentrations remains unresolved. Clinical evidence is concentrated in controlled photochemotherapy; support for other coumarins remains experimental. Further development requires chemically defined materials, appropriate comparators, measured skin exposure, and formulation-specific photosafety. Constituent activity alone does not validate traditional use; linking these results to traditional preparations requires preparation-matched comparisons of extracts and constituents.