French physician Joseph Honoré Simon Beau first described "Beau's lines," or transverse ridges -- horizontal grooves on the nail -- in 1846. Beau was best known for his research on the heart and lungs, but the nail community remembers him for noticing this condition.
Beau’s lines, as they have come to be known, occur when the nail matrix is injured and the growth of the nail is slowed. This eventually causes grooves in the surface of the nail plate. Affecting finger- and toenails, this condition is most commonly caused by an injury such as slamming a finger in the door or dropping a heavy object on a toe.
Transverse ridges can also be a sign of a systemic illness—an illness that affects the entire body rather than just one organ—or of a congenital disease, which means it was acquired during the body’s development in the uterus.
Whatever the reason for the slowing or halting of nail growth, it will result in transverse ridges on the nails, which look like pale bands lying horizontally across the nail plate. They first appear at the moon (lunula) and then progress with the growth of the nail. In cases where the ridges are not caused by a systemic illness or congenital disease, Beau’s lines will grow out with the nail and disappear.
Fingernails take approximately nine months—about one millimeter per week—to grow out completely, with the middle fingernail growing most rapidly, and toenails take approximately 18 months to grow out. With this in mind, by measuring the distance from the transverse groove to the cuticle, you can sometimes estimate the date of the injury or illness.
Beau’s lines are a result of a variety of conditions, ranging from minor to severe. The most common causes are local injury or exposure to severe cold, both of which decrease the blood flow to the nail matrix.
Any kind of injury to the nail matrix (also called a microtrauma) slows cell division in the matrix, causing transverse ridges to appear. An example is with athletes who do a lot of jogging or long-distance running—they often find Beau’s lines on their toenails from the repeated smashing of the distal edge into the front of the shoe when running or kicking.
But not all injuries are from playing sports; other examples of local traumas include:
Eczema The inflammation in the skin around the nail (the proximal fold) associated with eczema can prevent normal cell division in the nail matrix.
Habit-tic deformity (HTD) A source of repeated, habitual trauma to the nail matrix, HTD occurs when a person habitually picks at or rubs the central cuticle with a neighboring finger, most commonly seen on the thumb.
Subungual hematoma The hematoma can press into the nail matrix affecting nail cell production.
Paronychia Inflammation of the tissue adjacent to the nail, usually accompanied by infection and pus formation.
Onychia Inflammation of the matrix often leading to suppuration—or pus formation—and loss of the nail.
Carpal Tunnel Syndrome A condition caused by compression of the median nerve in the carpal tunnel, which can affect nail growth.
Another cause of Beau’s lines is congenital disease. Acrodermatitis enteropathica (technical jargon for zinc deficiency) causes changes in the skin and sometimes skin infections around the fingernail, which may result in ridges on the nail.
Beau’s lines are also caused by systemic illnesses, which include extreme fevers, measles, mumps, myocardial infarction and exposure to chemotherapy and radiation.
(Yes, this is a long list to remember, but there is good news—you don’t need to memorize all of these causes in order to help your clients.)
How To Treat Beau’s Lines
Despite the long list of causes, there are a few things you can do to help a client with Beau’s lines, and a few things your client can do to help herself.
The first step in preventing this condition from coming back is to refer your client to her doctor. In many cases, she may have a history of the above conditions. As a nail technician, you are not able to diagnose or treat her condition, but her doctor will be able to give her instructions on how to proceed.
After your client has seen her physician and gets the green light for a nail service, you then have a couple of options. Offer her a set of enhancements, especially if she considers the lines unappealing. But do not apply enhancements if the client has yet to see a doctor to evaluate the cause of the Beau’s lines.
You can also provide your client with a natural nail manicure and polish the nails with her favorite color. But be careful; the grooves on the nail mean there isn’t as much nail growth, so you don’t want to file the ridges in an attempt to smooth the nail, as this will cause further damage by making the nail very thin and fragile.
Beau’s lines are caused by a variety of conditions. As with every set of nails at your station that seems out-of-the-ordinary, you need to proceed with caution. The good news for you and your client is that these grooves won’t put an end to her nail services—it’s just a bit of a pause on the road to beautiful nails!
Beau's Lines Statistics
Cheryl Louise Branche is a retired M.D. living and working in New York as a consultant.