What causes a gray vertical line on the fingernail of the middle finger?

Gray vertical lines appearing on the fingernail of the middle finger are often associated with factors such as nail trauma, prolonged manicure stimulation, nail dystrophy, onychomycosis (fungal nail infection), and lichen planus. If the vertical line persists or widens, it is recommended to seek timely evaluation at a dermatology clinic in a formal medical facility. Specific causes are analyzed as follows:

1. Nail Trauma

External forces such as pressure or impact can cause capillaries beneath the nail to rupture and bleed, resulting in blood accumulation that appears as a gray vertical line. Avoid further injury to the nail, and maintain an appropriate nail length when trimming to protect the nail bed. The discoloration typically resolves spontaneously within 2–3 months as the nail grows out.

2. Prolonged Manicure Stimulation

Chemical components in gel nail polish may penetrate the nail plate, while the filing process damages the nail's protective barrier, leading to pigmentation and vertical lines. Discontinue manicures, clean nails daily with warm water, and apply hand cream containing vitamin E to moisturize the skin around the nails.

3. Nail Dystrophy

Deficiencies in nutrients such as vitamin A, calcium, and zinc can lead to abnormal keratinization of the nail plate, causing gray vertical lines, often accompanied by brittle, easily layered nails. Increase intake of foods like carrots, milk, and nuts, and take supplements as directed by a physician, including vitamin A soft capsules, calcium gluconate oral solution, and zinc gluconate oral liquid.

4. Onychomycosis (Fungal Nail Infection)

Fungal infection damages the nail plate structure, leading to pigment deposition and gray vertical lines, along with thickening and brittleness of the nail. Follow medical advice for topical treatment with terbinafine hydrochloride cream and oral antifungals such as itraconazole capsules or fluconazole tablets. Keep nails dry and clean.

5. Lichen Planus

An autoimmune condition affecting the nail matrix, disrupting normal nail growth and causing gray vertical lines, often accompanied by redness and itching of the skin around the nails. Under medical guidance, topical mometasone furoate cream may be used, along with oral acitretin capsules and hydroxychloroquine tablets. In severe cases, nail bed reconstructive surgery may be considered.

Routine care includes avoiding physical trauma to the nails and reducing frequency of manicures; maintaining a balanced diet to ensure adequate nutrition; frequent handwashing and avoiding sharing nail clippers to reduce infection risk; and regular monitoring of nail changes, seeking prompt medical attention if abnormalities occur.