Nail Separation (Onycholysis)

What nail separation looks like

The nail plate normally bonds tightly to the pink nail bed. In onycholysis:

• the nail lifts from the free edge back toward the cuticle, or less often from the sides
• the separated area looks white or opaque because air is trapped under it
• it may turn yellow from debris or green-black from bacteria (Pseudomonas)
• the boundary between attached and detached nail may be irregular
• it is usually painless

When the nail separates starting at the cuticle and the whole nail may shed, it is called onychomadesis, which often follows a fever, illness or hand, foot and mouth disease.

Causes of nail separation

Injury and mechanical stress

The most common cause. It includes:

• banging or crushing a finger, or a toe hitting the end of tight shoes during running or hiking
• long nails used as tools or levers
• aggressive cleaning under the nails or manicures that push back the cuticle hard
• typing or tapping with long acrylic nails

Moisture and irritants

Frequent hand-washing, cleaning, dishwashing, hairdressing and other wet work soften the nail and loosen the bond. Detergents, solvents and nail polish removers add to the damage.

Fungal infection

Onychomycosis commonly causes separation with thickening, yellowing and crumbly debris under the nail. It is more common in toenails.

Psoriasis

Nail psoriasis causes separation with a reddish-brown border, oil-drop spots (salmon patches), pitting and thickening. Several nails are often involved, and skin or joint psoriasis is usually present. See psoriatic nails.

Cosmetic products

Allergic or irritant reactions to nail glue, acrylic and gel nails, hardeners containing formaldehyde, and UV-cured gel polish can cause separation of several nails.

Medicines with sunlight (photo-onycholysis)

Some medicines make the nail bed sensitive to sunlight, causing separation after sun exposure. These include tetracycline antibiotics (especially doxycycline), psoralens, some NSAIDs, fluoroquinolones and certain chemotherapy drugs, such as taxanes.

Medical conditions

• Overactive thyroid (hyperthyroidism): typically affects the ring finger first. Called Plummer's nails.
• Pregnancy
• Iron deficiency, poor circulation and some connective tissue diseases
• Skin conditions such as eczema and lichen planus
• Tumors under the nail, such as warts, squamous cell carcinoma or, rarely, melanoma, which can cause separation of a single nail

How doctors find the cause

A doctor or dermatologist will ask about injuries, work, hobbies, nail cosmetics, new medicines, sun exposure and other symptoms, and examine all your fingernails, toenails and skin. Tests may include:

• nail clippings sent for fungal microscopy and culture
• thyroid blood tests if several nails are involved without a clear cause
• biopsy for a single persistent separation with a lump, bleeding or dark pigment

Treatment and care

The detached part of the nail cannot reattach. The goal is to remove the cause and let a healthy nail grow out.

• Trim the separated nail short, as far back as is comfortable. This removes the lever that pulls the nail further away and stops dirt collecting.
• Keep hands dry: wear cotton-lined rubber gloves for wet work, and dry thoroughly after washing.
• Do not clean under the nail with sharp tools.
• Avoid nail cosmetics (acrylics, gels, hardeners) until the nail regrows.
• Protect from sun if a medicine is the cause.
• Treat infection: antifungal treatment for confirmed fungus. A green nail from Pseudomonas often clears with keeping the nail short and dry, sometimes with a topical antiseptic or antibiotic solution.
• Treat psoriasis or thyroid disease, which allows normal regrowth.

How long it takes to heal

If separation persists for more than 6 months, the nail bed can become permanently scarred and the nail may never fully reattach, so early treatment of the cause matters.

Frequently asked questions

Will onycholysis reattach?

No. The lifted part of the nail will not stick back down. As the nail grows, a new, attached nail replaces it from the cuticle outward. Trimming the separated part and avoiding the cause gives the best chance of healthy regrowth.

What causes fingernails to separate from the nail bed?

The most common causes are minor injuries, long nails, frequent wet work, harsh cleaning products and nail cosmetics. Fungal infection, psoriasis, an overactive thyroid and some medicines combined with sunlight are other causes.

Is nail separation a sign of thyroid problems?

It can be. An overactive thyroid sometimes causes nail separation, often starting in the ring finger. If several nails lift without injury and you also have weight loss, heat intolerance, tremor or palpitations, ask your doctor for a thyroid blood test.

Why is the separated part of my nail green?

A green or green-black color under a lifted nail is usually caused by Pseudomonas bacteria that grow in damp spaces. Keeping the nail trimmed short and dry usually clears it. A doctor may suggest an antiseptic or antibiotic solution.

How long does it take for a separated toenail to grow back?

A toenail grows slowly and takes 12 to 18 months to grow out completely. Fingernails take about 4 to 6 months. Keep the area clean and dry and wear roomy shoes while it regrows.