What is the primary cause of leukonychia?

Leukonychia, characterized by white spots or lines appearing on the nails, is most commonly caused by physical injury to the nail matrix. When the nail matrix, the tissue under the base of the nail that eventually forms the nail plate, is injured, it can disrupt the production of keratin, resulting in the formation of these white areas. Such injuries can occur from various activities or trauma, leading to localized damage that manifests as leukonychia.

While other factors like chemical exposure or infections can impact nail health, they do not primarily result in leukonychia. Chemical exposure might lead to discoloration or other nail conditions, infections could result in redness or pus, and genetic factors could predispose individuals to various nail conditions, but they are not the primary cause of this specific issue. Hence, focusing on physical injury helps in understanding the most common and direct source of leukonychia in practice.