Maidenhair fern (Adiantum capillus-veneris) is a delicate fern that shows up in older herbal traditions. People once used it as a mild ingredient in teas and tinctures, but nobody uses it much anymore. No solid evidence backs any particular health claim.
The plant occasionally gets brewed as an herbal tea or processed into an extract. The active compounds and how they might work remain unclear. Mainstream research has not mapped out its constituents or mechanisms.
Major health authorities do not recognize any established therapeutic use for this herb.