Black Nightshade (Solanum nigrum) has a long history of use in traditional medicine systems across the world, including Ayurveda, Unani, and various folk remedies. In some regions, its leaves or juice have been reportedly used as a topical application to treat lice infestations. The rationale has generally stemmed from its reputed insecticidal and antiparasitic properties, which are recognized in traditional herbal medicine literature.

However, modern scientific studies directly evaluating Black Nightshade's efficacy or safety for treating head lice (Pediculus humanus capitis) are lacking. There are no clinical trials or robust laboratory studies confirming its activity against lice or its comparative effectiveness to standard treatments like permethrin or malathion. Some phytochemical analyses show that Black Nightshade contains alkaloids and other compounds with potential insecticidal effects, but these are not specific to lice and have not been tested in the context of human infestation. Furthermore, Black Nightshade is known to be toxic if ingested or improperly used, raising safety concerns.

In summary, while Black Nightshade has a basis in traditional use for lice, there is little to no scientific validation for this purpose. Its use should be approached with caution due to safety concerns, and modern, evidence-based treatments are strongly preferred.