Traditional Chinese medicine-related interventions for allergic conjunctivitis and vernal keratoconjunctivitis: clinical evidence, mechanistic hypotheses, and ocular surface safety considerations.

Allergic conjunctivitis (AC) and vernal keratoconjunctivitis (VKC) are immune-mediated ocular surface diseases in which itching, conjunctival hyperemia, tearing, mucus secretion, epithelial injury and recurrence may substantially affect comfort and quality of life. Standard care is based on allergen avoidance, lubricants, topical antihistamines, mast-cell stabilizers, corticosteroids and topical immunomodulators when clinically indicated. Traditional Chinese Medicine (TCM) modalities are used in some clinical settings as adjunctive strategies, but their evidence base is heterogeneous and should not be interpreted as a substitute for established ophthalmic therapy. This structured narrative review synthesizes ocular clinical evidence, indirect mechanistic evidence and ocular surface safety considerations for TCM modalities in AC and VKC. Five bibliographic databases-PubMed/MEDLINE, Web of Science Core Collection, CNKI, Wanfang Data and VIP Database-were searched for literature published from 1 January 2010 to 31 May 2026. The database searches were supplemented by targeted Google Scholar searches, reference-list screening and citation tracking, while earlier landmark sources were retained when clinically or mechanistically relevant. The retrieved clinical evidence was concentrated in AC/SAC/PAC and VKC. No eligible AKC- or GPC-specific TCM clinical studies were identified within the search scope; these conditions are therefore discussed only for contextual and safety relevance. Oral herbal formulas and integrated TCM-standard therapy accounted for most of the clinical evidence, whereas herbal ophthalmic preparations, particularly Houttuynia eye drops, provided a smaller but more ocular-specific signal. Mechanistic claims involving IgE-mast-cell responses, Th2/eosinophilic inflammation, epithelial alarmins, NF-κB/NLRP3 signaling, oxidative stress and barrier dysfunction should be regarded as hypotheses requiring ocular-specific validation. For local herbal ophthalmic preparations, the safety threshold is high and includes sterility, endotoxin control, pH, osmolality, particulate matter, preservatives, botanical authentication, formulation stability and corneal epithelial safety. Adequately powered clinical studies using standardized diagnostic criteria, validated ophthalmic outcomes, longer follow-up periods, and prospective safety monitoring are needed to strengthen the evidence base.