Nail ridges: vertical and horizontal lines on fingernails and what they mean

Nail ridges are raised or sunken lines in the nail plate. Because the nail is made by the nail matrix, a small area of tissue beneath the proximal nail fold, any disturbance of the matrix can show up as a mark that grows out with the nail. The PCDS divides ridges into longitudinal ridges, which run along the length of the nail, and transverse ridges, which run across it.

The NHS notes that nail problems are not usually caused by anything serious, and that nails change over time. They commonly become thicker or more brittle with age and can change during pregnancy. Most people who notice faint vertical ridges are seeing a normal feature of their nails.

The PCDS says a few ridges are seen in normal nails. When ridging is more marked or has changed, the PCDS lists several possible causes.

Lines across the nail often reflect a temporary interruption of nail growth, or damage to the area at its base. The PCDS lists several causes.

• Beau's lines: horizontal grooves in the nail plate that occur when nail growth temporarily slows, for example after infection, trauma or systemic illness.

• Onychomadesis: similar growth arrest, but the full thickness of the nail is involved, causing the nail plate to separate from the nail bed. It most frequently occurs several months after hand, foot and mouth disease but can follow other viral infections.

• Eczema: can cause irregular transverse ridging, with thickening and sometimes discolouration.

• Chronic paronychia: inflammation of the nail fold, which can cause transverse ridging as well as discolouration and onycholysis.

• Artificial nails: the PCDS says nail cosmetic dystrophy from artificial nails can cause ridging, onycholysis and marked thinning of the nail.

The NHS says to see a GP if a nail has changed shape, changed colour or fallen off and you do not know why, or if the skin around a nail has become sore, red, swollen and warm, which can be a sign of infection. Because the PCDS notes that nail lichen planus can cause permanent damage, a GP referral to dermatology is sensible when ridging is accompanied by thinning, splitting or loss of the nail, or when it affects several nails and keeps progressing.

Dark streaks need separate attention. The PCDS says that a new, changing, solitary black, brown or occasionally red line in the nail should raise the possibility of subungual melanoma, and that patients with suspected melanoma should be referred urgently to secondary care. This is a different problem from ridges but is worth being aware of when you are looking closely at your nails.

The NHS suggests wearing rubber gloves if your hands are often in water or you regularly use cleaning products, applying hand cream to nails and fingertips regularly, trimming nails straight across, not biting or picking nails or the skin around them, and not cleaning under nails with sharp objects. The PCDS general measures include protecting hands from solvents and other chemicals, using plenty of emollients, avoiding soap and avoiding manicures.

If a habit such as picking or rubbing the cuticle is causing ridges, the PCDS says habit-tic nail deformity generally responds well to habit reversal, although long-term damage can sometimes leave permanent changes. If a ridge came from illness or injury, it will usually grow out and no treatment is needed, because the affected part of the nail moves forward as the nail grows.

Nail ridges are usually assessed by a GP, and the NHS says some people can refer themselves directly to a podiatrist for nail problems without seeing a GP, depending on local services. Dermatology referrals are made when the cause is unclear, or when lichen planus, psoriasis or a suspicious pigmented line is considered. Private dermatology or podiatry appointments can be quicker, but cosmetic treatments are unlikely to change ridges that come from an underlying condition.