Trauma or injury
Physical trauma or injury to the nail or nail bed can cause vertical ridges to appear. This is usually temporary and goes away as the nail grows.

Causes of horizontal lines
Severe illness or stress
Beau’s lines can appear after the body experiences severe stress or illness, such as a high temperature, infection, or major surgery. These lines indicate a temporary interruption in nail growth.

Nutritional deficiency
Like vertical lines, horizontal lines can also be a sign of nutritional deficiency. Ensuring adequate intake of essential vitamins and minerals is important for healthy nails.

Medical conditions
Chronic conditions such as diabetes, heart disease, and respiratory disease can cause Beau’s lines. These lines often reflect the severity and duration of the underlying condition.

Medications and chemotherapy
Some medications, especially chemotherapy drugs, can affect nail growth and lead to horizontal lines.

Diagnosis and when to see a doctor
Symptoms and warning signs
Not all lines on the nails are a cause for concern, but some symptoms require a visit to the doctor. These include changes in nail color, pain, swelling, or the presence of multiple horizontal lines.

Diagnostic tests
Doctors may perform various diagnostic tests to determine the cause of the lines on your nails. These can include blood tests, imaging studies, and a biopsy of the nail bed.