What causes vertical lines on fingernails?

Vertical ridges on the fingernails—also known as longitudinal ridges or nail striations—are linear, raised lines that run from the cuticle to the fingertip. In most cases, these ridges are a normal, age-related change. As people grow older—typically beginning in their 40s or 50s—the nail matrix (the tissue beneath the proximal nail fold responsible for nail growth) gradually becomes less uniform in its cell production, leading to subtle irregularities in nail plate formation. This results in fine, asymptomatic vertical ridges that are often more noticeable on the index and middle fingers.

While benign aging is by far the most common cause, certain medical conditions may contribute to or exacerbate vertical ridging. These include iron deficiency anemia, hypothyroidism, and nutritional deficiencies—particularly of B vitamins (e.g., biotin), zinc, or protein. Chronic inflammatory skin conditions such as lichen planus or psoriasis can also affect the nail matrix and produce ridging, sometimes accompanied by other signs like pitting, discoloration, or onycholysis (separation of the nail from the nail bed). Additionally, trauma—repetitive minor injury to the nail folds or matrix—may induce temporary ridging as the nail regenerates.

It’s important to distinguish vertical ridges from horizontal ridges (Beau’s lines), which reflect transient systemic stressors such as severe illness, high fever, chemotherapy, or acute malnutrition. Unlike Beau’s lines, vertical ridges rarely indicate serious underlying disease when they appear gradually and symmetrically without associated symptoms.

If vertical ridges are new, rapidly worsening, asymmetric, or accompanied by other concerning features—including nail thickening, brittleness, color changes (e.g., dark longitudinal streaks), splitting, pain, or skin/mucosal changes—a dermatologic evaluation is warranted to rule out pathologic causes. Otherwise, routine monitoring and supportive nail care—such as gentle moisturizing of the cuticles and avoiding excessive filing or harsh chemicals—can help maintain nail integrity.