Horizontal Lines
Horizontal ridges, also known as Beau’s lines, are considered a symptom of more serious diseases. These indentations on the nail surface can impede nail growth until the underlying condition is detected and treated.
Beau’s lines are an indication of acute kidney disease, and when they develop on all 20 nails, they suggest the presence of mumps, thyroid disease, diabetes, or syphilis. According to a study published in Acta Haematologica, they also appear in patients undergoing chemotherapy.
A blow or trauma is another reason why red or brown spots develop under the nails. It’s important to be very careful not to confuse these changes in color with symptoms of diseases such as endocarditis or melanoma. In those cases, you should be alert for a dark brown, black, or red color.
