What is a common cause of nail discoloration?

Nail discoloration can often be traced back to exposure to chemicals, which aligns with the correct answer. Chemicals found in household products, nail polish removers, and even certain nail products can lead to changes in the color of the nails. For instance, strong solvents and other harsh substances can cause browning, yellowing, or even greenish hues, especially if there is prolonged or repeated contact.

In contrast, while insufficient hydration may impact the overall health and appearance of the nails, it typically does not cause discoloration on its own. Overuse of hand lotion might result in an oily appearance or a build-up on the nails, but not a significant change in color. Frequent filing is more associated with changes in nail texture or strength rather than color. Therefore, the link between chemical exposure and nail discoloration makes it the most relevant and accurate answer in this context.