Mees lines are white lines or bands that appear on the fingernails or toenails, running across the nails from side to side, parallel with both the cuticles and the white tops of the nails. They usually run the entire width of the nail and start at the bottom, closest to the cuticles, and then move toward the top of the nail over time. Mees lines are a true leukonychia with single or multiple white transverse lines running across the width of the finger and toe nails, parallel to the lunula. They are a color change of the nail with no palpable ridges and usually have no nail surface irregularity. They can be seen but not felt, and they progress with the growth of the nail. Mees lines do not disappear with nail bed pressure, and they are differentiated from true leukonychia due to trauma as they appear on several nails simultaneously, involve the entire width of the nail, and have a contour similar to that of the lunula.
Mees lines are often a symptom of an underlying health problem, such as arsenic poisoning or kidney failure. They have also been observed in chemotherapy patients. Historically, Mees lines have been associated with poisoning from arsenic or other heavy metals, such as thallium or selenium. Mees lines can appear on only one nail or all nails at the same time, and they eventually grow out, so the lines themselves disappear.
There is no information available on the ingredients or materials that cause Mees lines.
