Which factor can contribute to the development of Beau's lines?

Beau's lines are noticeable horizontal ridges that can develop across the nail plate, and they are often a sign of a temporary interruption in nail growth. The correct answer indicates that an illness or injury can lead to a disturbance in the nail matrix, slowing down its growth and causing the appearance of these lines. When the nail matrix is injured or affected by illness, it interrupts the normal production of keratin, which is essential for nail growth. As a result, the growth is stunted, leading to the formation of Beau's lines as the nail grows out.

In the context of other factors, while nutrition deficiencies can affect overall health and potentially impact nail growth, they do not directly cause Beau's lines in the same manner as an illness or injury. External nail polish applications, on the other hand, do not have a direct influence on the growth of the nail matrix, and genetic predisposition might contribute to various nail conditions but is not a direct cause of the horizontal lines associated with Beau's lines. Understanding these distinctions clarifies why the interruption of the nail matrix due to illness or injury is the most relevant factor in the development of Beau's lines.