What is a common sign of nail infection?

Discoloration and swelling are common and significant signs of a nail infection. When an infection occurs, it often leads to a change in the coloration of the nail, which can manifest as a yellow, green, or darkened appearance. This discoloration is accompanied by swelling around the area, indicative of inflammation and the body's response to the infection. This reaction is the immune system's way of attempting to fight off the invading pathogens, leading to these visible symptoms.

In contrast, other choices do not effectively indicate an infection. For example, color loss may suggest other issues like dehydration or nutritional deficiencies rather than an infection. Improved shine might reflect healthy nail care and maintenance rather than any signs of infection. Increased length isn’t associated with infections, as nails typically grow regardless of any underlying issues, and longer nails do not imply a healthy or infected state. Thus, the combination of discoloration and swelling is a clear indicator of a nail infection, making it the most accurate answer to identify such a condition.