Trichomegaly is a condition where there is an increase in the length and thickness of eyelash hair. It can be congenital, acquired, or drug induced.

Elongated and thicker eyelashes are frequently present in children with rare congenital syndromes such as Oliver-McFarlane syndrome and Cornelia de Lange syndrome.

Acquired disorders such as human immunodeficiency virus (HIV) infection, atopic dermatitis, allergic rhinitis, uveitis, and vernal keratoconjunctivitis may also be associated with trichomegaly.

Drugs that are commonly associated with eyelash growth are prostaglandin analogs, epidermal growth factor receptor inhibitors (EGFRIs), and MEK inhibitors, and less commonly interferon-alpha and cyclosporine.