Horizontal ridges on toenails, often referred to as Beau’s lines, appear as indentations or grooves that run across the nail plate. These transverse lines indicate a temporary interruption or slowdown in the nail’s growth process. The nail matrix, located under the cuticle, is where new nail cells are produced, and any disruption to this area can lead to the formation of these ridges. While their appearance might seem concerning, Beau’s lines typically signify an event that occurred in the past, rather than an ongoing problem. As the nail grows, these ridges slowly move towards the tip, eventually growing out over several months.
Physical Stressors and Injury
Physical trauma or stress to the nail matrix, located beneath the cuticle where nail growth originates, can disrupt normal nail formation. An acute impact, such as stubbing a toe or dropping a heavy object, can temporarily halt new nail cell production. This interruption forms a visible indentation across the nail plate, marking the injury.
Ill-fitting footwear that exerts chronic pressure on the toes is another common physical stressor for toenails. Constant compression can repeatedly injure the nail matrix, leading to the formation of Beau’s lines over time. This ongoing microtrauma can create multiple ridges if the pressure is sustained or recurs. Aggressive nail care practices, including vigorous pushing or cutting of cuticles, or improper pedicures, can also inflict trauma on the delicate nail matrix.
The ridge forms at the time of the injury and gradually moves forward with the growing nail plate. Since toenails grow at a rate of approximately 1 millimeter per month, a ridge caused by a specific event might take several months, often 6 to 12 months, to grow out completely and disappear from the nail. The depth of the ridge can indicate the severity of the disruption to nail growth.
Underlying Medical Conditions
Various systemic health issues or acute illnesses can temporarily halt or slow nail growth, resulting in horizontal ridges. Acute illnesses, particularly those with high fevers or severe infections like pneumonia, mumps, or measles, can cause the body to temporarily redirect energy away from nail formation. Significant physiological stress, such as a heart attack or major surgery, can similarly induce these lines.
Chronic conditions can also contribute to Beau’s lines by interfering with blood flow to the nail matrix or disrupting metabolic processes. Uncontrolled diabetes, for instance, can lead to these marks due to elevated blood sugar levels impacting nail growth. Peripheral artery disease (PAD), which reduces circulation to the extremities, can similarly compromise nail production. Thyroid disorders, whether hyperthyroidism or hypothyroidism, can also manifest nail changes, including ridges, due to their impact on metabolism.
Kidney disease, particularly acute kidney failure, can interrupt nail growth, leading to Beau’s lines. Liver disease is another systemic condition associated with nail changes. Inflammatory skin conditions affecting the nail matrix, such as psoriasis or eczema, can also cause horizontal ridges by disrupting cell division. The number and depth of the ridges can offer clues about the severity or recurrence of the underlying condition.
Nutritional Gaps and Medications
Deficiencies in essential nutrients and the side effects of certain medications can interfere with healthy toenail growth, leading to horizontal ridges. The nail matrix requires a steady supply of specific vitamins and minerals for continuous nail cell production. A lack of essential nutrients like zinc, iron, or protein, crucial for healthy nail formation, can disrupt this process. Zinc deficiency, for example, can impact cell proliferation in the nail matrix. Inadequate protein intake can also cause these ridges.
Certain medications are known to cause horizontal ridges as a side effect. Chemotherapy agents, for instance, are a primary cause of Beau’s lines due to their impact on nail matrix cells. Each chemotherapy infusion can temporarily arrest nail growth, leading to a distinct ridge. Other medications, such as retinoids and some antibiotics, can also interfere with nail matrix processes, causing temporary growth interruptions. Once the nutritional deficiency is corrected or the medication course is completed, new nail growth should proceed normally, and existing ridges will eventually grow out.