Lines and other findings in the fingernails are generally benign but can be caused by many medical conditions, including some that require treatment. Physicians who would be best qualified to evaluate your child include your pediatrician
or your dermatologist
Lines in the fingernails can have many causes. If there is a history of trauma, such as a finger slammed in a car door, then this is the most likely possibility, and the line will disappear as the nail regenerates and grows out.
Occasionally, remnants or damage from nail products, such as nail polish strippers or false nail adhesives can cause linear damage to the nail.
Beau's lines are the name of short, red, horizontal depressions in the growth of the nail. These lines are caused by a serious medical illness
that temporarily disrupts the healthy nail growth. They are common in persons who have just recovered from a serious medical illness or hospitalization. However, they can also occur in situations such as eating disorders or other causes of serious malnutrition.
As always, the diagnosis and management of your child's condition will require a physical examination by your personal physician. Scheduling an appointment or office visit with your pediatrician or dermatologist is recommended.