Eyelash extension procedures may cause ocular disorders, such as keratoconjunctivitis and allergic blepharitis; indeed, all glues for eyelash extensions analyzed in the present study contained formaldehyde, which can cause keratoconjunctivitis. From the viewpoint of hygienics, it is necessary to disinfect devices, provide handling instructions for organic solvents, improve glue ingredients, and improve the ophthalmologic knowledge of the practitioners.