Onycholysis

Onycholysis is the painless separation of the nail plate from the underlying nail bed. It usually starts at the free edge (tip) of the nail and progresses toward the base. The separated portion of the nail appears white or yellowish because air fills the space between the nail plate and the nail bed.

Onycholysis is not a disease itself but a sign that can result from many different causes — including trauma, skin conditions like psoriasis, fungal infections, certain medications, and occasionally thyroid or other systemic diseases. It is one of the most common nail complaints seen by dermatologists and affects fingernails more often than toenails.

In most cases, onycholysis is harmless and reversible once the underlying cause is identified and addressed. However, the detached nail creates a moist, enclosed space that is prone to secondary infections, particularly by yeast (Candida) or bacteria (Pseudomonas), which can cause the nail to turn green or develop an unpleasant odor.

• White or yellowish area: The detached portion of the nail appears white, opaque, or yellow-white, in contrast to the normal pink nail
• Starts at the tip: Separation typically begins at the free (distal) edge and extends backward toward the base of the nail
• Smooth border or irregular border: Depending on the cause, the line where normal and detached nail meet may be smooth or jagged
• Nail surface: The nail plate itself may appear normal or may show additional changes (pitting, ridging, thickening) depending on the cause
• Color changes: A green discoloration suggests bacterial infection (Pseudomonas); yellow-brown may suggest fungal infection; hemorrhagic spots suggest drug-related causes

• Fingernails: Most commonly affected, especially the ring finger and long (middle) finger of the dominant hand
• Toenails: Frequently affected by trauma-related and fungal onycholysis, particularly the great toenail
• Single nail vs. multiple nails: Trauma usually affects one or two nails; psoriasis, medications, and systemic causes tend to involve several or all nails
• Pattern: Distal onycholysis (starting at the tip) is most common; lateral onycholysis (starting from the side) is also seen, particularly in psoriasis

Onycholysis may be accompanied by:

• Subungual hyperkeratosis: Buildup of white or yellow scales beneath the nail (common in psoriasis and onychomycosis)
• Nail pitting or ridging: Small depressions or lines on the nail surface (psoriasis, eczema)
• Nail discoloration: Green (Pseudomonas infection), yellow-brown (fungal), oil-drop spots (psoriasis)
• Skin changes: Psoriatic plaques on the body, dermatitis on the hands, or fungal infection between the toes
• Pain: Onycholysis itself is typically painless; pain suggests secondary infection, subungual tumor, or glomus tumor
• Odor: An unpleasant smell may indicate secondary bacterial or yeast infection in the detached space

Consider medical evaluation for:

• Onycholysis affecting multiple nails without a clear cause (such as trauma) — this may signal psoriasis, thyroid disease, or another systemic condition
• Green, yellow, or brown discoloration of the detached area, suggesting infection
• Pain, swelling, or tenderness in the affected nail — pain under a nail with onycholysis may indicate a subungual tumor
• Onycholysis that does not improve after several months despite avoiding trauma and irritants
• New nail separation after starting a medication, especially antibiotics (tetracyclines, fluoroquinolones) combined with sun exposure
• Onycholysis in a single nail that is slowly progressive and unresponsive to treatment — chronic unexplained onycholysis in a single nail may rarely indicate subungual squamous cell carcinoma

Onycholysis (from Greek onycho-, nail, and lysis, loosening) is defined as the distal or distal-lateral separation of the nail plate from the underlying nail bed and/or the hyponychium, without complete shedding of the nail. The separated portion of the nail plate appears white or opaque due to the presence of air beneath the detached plate. Onycholysis is the most common cause of apparent nail whiteness and is a nonspecific sign associated with a wide range of local, dermatologic, systemic, and iatrogenic causes.

By anatomical pattern

• Distal onycholysis: Separation begins at the free edge of the nail and extends proximally. The most common pattern; typical of trauma, onychomycosis, and psoriasis
• Lateral onycholysis: Separation along one or both lateral margins of the nail plate. Seen in psoriasis, warts, and foreign body reactions
• Proximal onycholysis: Rare; separation begins at the lunula region. Associated with systemic disease, chemotherapy, and Raynaud phenomenon
• Photo-onycholysis: A photosensitivity-mediated variant; separation often presents as a semilunar or oval detachment with variable pigmentation

By etiology

• Traumatic: Mechanical trauma, repetitive microtrauma, manicure injury, ill-fitting footwear, occupational trauma, nail cosmetics
• Inflammatory/dermatologic: Psoriasis (most common dermatologic cause), lichen planus, eczematous dermatitis (atopic, contact), alopecia areata
• Infectious: Onychomycosis (dermatophytes, non-dermatophyte molds), Candida, Pseudomonas aeruginosa (secondary colonizer), bacterial infection
• Drug-induced: Photo-onycholysis (tetracyclines, fluoroquinolones, psoralens, NSAIDs), chemotherapy-induced (taxanes, anthracyclines), retinoids, antipsychotics
• Systemic: Thyroid disease (especially hyperthyroidism — Plummer's nails), iron deficiency anemia, peripheral vascular disease, diabetes mellitus, yellow nail syndrome, connective tissue diseases
• Neoplastic: Subungual squamous cell carcinoma, melanoma, glomus tumor, onychomatricoma — must be considered in chronic single-digit onycholysis unresponsive to treatment
• Idiopathic: A proportion of onycholysis cases, particularly in women, have no identifiable cause and are classified as idiopathic. These predominantly affect the fingernails and often have a chronic, relapsing course.

Epidemiology

Onycholysis is one of the most common nail disorders in clinical practice. It is more prevalent in women than in men, with a female-to-male ratio of approximately 2:1. It can occur at any age but is most frequently seen in adults. The fingernails are affected more often than the toenails, and the ring finger and long finger of the dominant hand are the most commonly involved digits in idiopathic and traumatic onycholysis.

Nail bed psoriasis is the most common dermatologic cause, with onycholysis reported in 34% of patients with psoriatic nail disease. Onychomycosis is the most common infectious cause and may coexist with primary onycholysis of other etiologies.

General features

The hallmark of onycholysis is a visible white or opaque zone at the distal end of the nail, where the nail plate has detached from the nail bed. The line of separation may be regular (smooth, linear) or irregular (jagged, serrated), and its morphology provides diagnostic clues:

• Smooth, linear border: Characteristic of traumatic onycholysis
• Irregular, erythematous border with oil-drop sign: Suggestive of psoriasis
• Jagged proximal border with yellow-white spikes: Suggestive of onychomycosis
• Semilunar or oval detachment with pigmentation: Photo-onycholysis

The nail plate overlying the onycholytic area is usually intact and of normal thickness, unless the underlying cause also affects the nail matrix (as in psoriasis, where pitting, ridging, and crumbling may coexist).

Photo-onycholysis

Photo-onycholysis is a rare photosensitivity reaction in which the nail plate separates from the nail bed following exposure to UV radiation in the context of a photosensitizing agent. It typically manifests more than two weeks after drug exposure and may follow a cutaneous photosensitivity reaction or occur as an isolated nail phenomenon. One or more fingernails may be affected. The detachment area often has a semilunar or oval shape with variable brownish pigmentation.

Drugs most frequently implicated:

• Tetracyclines (doxycycline, minocycline)
• Fluoroquinolones
• Antifungal agents (griseofulvin, voriconazole)
• NSAIDs (diclofenac)
• Psoralens (PUVA therapy)
• Targeted anticancer agents
• Topical aminolevulinic acid (photodynamic therapy)
• Antipsychotic drugs

Photo-onycholysis may also occur in the setting of photosensitive blistering disorders such as porphyria cutanea tarda and pseudoporphyria.

Psoriatic onycholysis

Psoriasis is the most common dermatologic cause of onycholysis. Onycholysis in psoriasis originates from the nail bed (not the matrix) and is often accompanied by other nail bed signs including oil-drop discoloration (salmon patch), subungual hyperkeratosis, and splinter hemorrhages. One or more nails may be involved, and onycholysis may be the only manifestation of nail psoriasis, making diagnosis challenging when skin plaques are absent.

Dermoscopy of the hyponychium reveals irregularly distributed, dilated, tortuous capillaries resembling those seen in cutaneous psoriatic plaques — a valuable diagnostic clue when onycholysis is the only finding.

Onychomycosis-associated onycholysis

Distal-lateral subungual onychomycosis is the most common pattern. It begins with distal onycholysis and subungual hyperkeratosis and progresses proximally. The nail plate may become thickened, yellow-brown, and friable. Dermatophytes (Trichophyton rubrum, T. mentagrophytes) are the most common pathogens. KOH preparation, fungal culture, or nail plate biopsy with PAS stain are indicated to confirm the diagnosis before initiating antifungal therapy.

Onycholysis from any cause predisposes to secondary fungal colonization, so a positive fungal culture does not always confirm onychomycosis as the primary etiology.

The nail plate is firmly attached to the nail bed through interdigitations between the ventral nail plate and the nail bed epithelium (rete ridges). Onycholysis occurs when this attachment is disrupted.

Traumatic mechanisms: Mechanical forces (direct impact, repetitive shearing, leverage from long nails) physically separate the nail plate from the bed. Once separated, the space fills with air and debris, preventing reattachment. Moisture and irritants (water, soap, chemicals) entering the onycholytic space worsen the detachment and promote secondary infection.

Inflammatory mechanisms: In psoriasis and lichen planus, inflammatory infiltrates in the nail bed disrupt the normal dermoepithelial interface. In psoriasis, the nail bed epithelium undergoes the same parakeratotic changes as psoriatic skin, with accumulation of parakeratotic scales that push the nail plate away from the bed.

Infectious mechanisms: Dermatophytes invade the nail bed epithelium, producing keratinases that break down the attachment between the nail plate and bed. Subungual hyperkeratosis results from the host's hyperproliferative response.

Drug-induced mechanisms: In photo-onycholysis, photosensitizing drugs are deposited in the nail bed, and UV exposure triggers a phototoxic reaction with blistering and separation at the nail bed–nail plate interface. In chemotherapy-induced onycholysis (particularly taxanes), inflammation of the nail bed from the cytotoxic agent leads to detachment.

Vascular mechanisms: In hyperthyroidism (Plummer's nails), increased distal blood flow and altered nail bed vasculature may contribute to onycholysis.

Nail bed biopsy is rarely performed for onycholysis alone but may be indicated in chronic, unexplained, single-digit cases to exclude neoplasia.

• Psoriatic onycholysis: Psoriasiform hyperplasia of the nail bed epithelium with parakeratosis, neutrophilic infiltrates, and dilated, tortuous capillaries in the nail bed dermis
• Onychomycosis: PAS-positive hyphae within the nail bed and ventral nail plate; parakeratosis and spongiosis of the nail bed epithelium
• Subungual squamous cell carcinoma: Atypical squamous epithelial proliferation with invasive features; must be considered in chronic single-digit onycholysis unresponsive to treatment
• Lichen planus: Lichenoid band-like lymphocytic infiltrate at the dermoepithelial junction of the nail bed, with basal layer vacuolar degeneration

Common mimics

• Normal free edge: The natural white free edge of the nail beyond the hyponychium should not be confused with pathological onycholysis
• Leukonychia: White discoloration of the nail plate itself (true leukonychia) — distinguished by the fact that the nail plate remains attached to the bed; does not blanch with pressure
• Onychomadesis: Complete proximal detachment of the nail plate from the matrix, resulting in nail shedding — represents a more severe insult than onycholysis

Must-not-miss diagnoses

• Subungual squamous cell carcinoma: Must be considered in chronic, unexplained onycholysis of a single nail unresponsive to treatment. Biopsy is indicated
• Subungual melanoma: Especially when onycholysis is accompanied by pigmentation or nail dystrophy
• Glomus tumor: Subungual tumor that may present with onycholysis and localized pain; diagnosed with MRI and biopsy

By dermoscopy

• Psoriatic onycholysis: Dilated, tortuous capillaries at the hyponychium (≥40x); red dots at lower magnification
• Hemorrhagic onycholysis (drug-induced): Abundant splinter hemorrhages and blood suffusion within the onycholytic area — characteristic of taxanes and photo-onycholysis
• Pseudomonas colonization: Bright green color on dermoscopy within the onycholytic space
• Onychomycosis (toenails): Jagged proximal border of the onycholytic area with yellow-white spikes projecting into the proximal nail plate; "ruined appearance" at the distal free edge
• Traumatic onycholysis (toenails): Linear, sharp proximal border of the onycholytic area; small hemorrhages within the detached zone

Frequently associated

• Trauma: The most common cause of onycholysis overall; repetitive microtrauma, occupational exposure, manicure, ill-fitting footwear
• Psoriasis: Onycholysis is the most common nail bed manifestation; found in ~34% of patients with nail psoriasis
• Onychomycosis: The most common infectious cause; often coexists with onycholysis of other etiologies as a secondary colonizer
• Contact dermatitis: Irritant or allergic contact dermatitis from nail cosmetics (acrylates, formaldehyde, nail polish), cleaning agents, or occupational chemicals

Occasionally associated

• Hyperthyroidism: Plummer's nails — distal onycholysis, classically of the fourth and fifth fingernails, described in hyperthyroid patients
• Hypothyroidism: May cause brittle nails with onycholysis
• Drug-induced photo-onycholysis: Tetracyclines, fluoroquinolones, psoralens, NSAIDs, antifungals
• Chemotherapy: Taxanes (paclitaxel, docetaxel) most frequently; also anthracyclines, 5-fluorouracil
• Lichen planus: Nail lichen planus with onycholysis, ridging, and thinning
• Yellow nail syndrome: Slow-growing, thickened, yellow nails with onycholysis, associated with lymphedema and pleural effusions
• Iron deficiency anemia: May contribute to nail fragility and onycholysis

Syndromic associations

• Yellow nail syndrome: Triad of yellow, thickened nails with onycholysis + lymphedema + pleural effusions
• Plummer's nails: Onycholysis in the context of Graves' disease or hyperthyroidism
• Nail-patella syndrome: Genetic disorder with nail hypoplasia and onycholysis, absent or hypoplastic patellae, and nephropathy

History taking

Essential questions:

• Onset: When was the nail separation first noticed? Acute vs. gradual?
• Progression: Stable or spreading? One nail or multiple?
• Trauma: Occupation (wet work, chemicals, manual labor), manicure habits, nail cosmetics, nail biting?
• Medications: Antibiotics (tetracyclines, fluoroquinolones), chemotherapy, retinoids? Timeline relative to onycholysis onset?
• Sun exposure: Combined with new medication? (photo-onycholysis)
• Skin diseases: Known psoriasis, eczema, lichen planus? Skin lesions elsewhere?
• Systemic symptoms: Weight changes, heat/cold intolerance, tremor (thyroid disease)? Fatigue, swelling (iron deficiency, liver disease)?
• Infections: Athlete's foot, history of fungal nail infections?
• Family history: Psoriasis, thyroid disease?

Physical examination

Systematic approach:

• Pattern of onycholysis: Distal, lateral, proximal, or semilunar (photo-onycholysis)
• Border morphology: Smooth (trauma), irregular with oil-drop sign (psoriasis), jagged with spikes (onychomycosis)
• Number of nails involved: Single (trauma, tumor) vs. multiple (psoriasis, medications, systemic)
• Associated nail changes: Pitting, ridging, subungual hyperkeratosis, splinter hemorrhages, nail thickening
• Color of onycholytic space: White (air), green (Pseudomonas), yellow-brown (fungal), hemorrhagic (drug-induced)
• Skin examination: Psoriatic plaques, eczematous patches, tinea pedis, lichen planus lesions
• Dermoscopy (onychoscopy): Examine the nail plate and hyponychium; assess border morphology, vascular patterns, hemorrhages, color

Diagnostic tests

• KOH preparation and fungal culture: Indicated whenever onychomycosis is suspected; sample subungual debris from the most proximal edge of onycholysis
• Nail clipping with PAS stain: More sensitive than KOH for onychomycosis; recommended when cultures are negative but clinical suspicion remains
• Dermoscopy: Aids differential diagnosis of psoriatic, traumatic, infectious, and drug-induced onycholysis (see Dermoscopic features above)
• Thyroid function tests: When multiple fingernails show onycholysis without a clear local cause, especially with systemic symptoms
• Complete blood count and iron studies: If pallor, fatigue, or brittle nails suggest iron deficiency
• Patch testing: When allergic contact dermatitis to nail cosmetics or occupational chemicals is suspected
• Nail bed biopsy: Reserved for chronic, single-digit onycholysis unresponsive to treatment — to exclude subungual squamous cell carcinoma, melanoma, or glomus tumor
• MRI of the digit: If a subungual glomus tumor is suspected (localized pain, cold sensitivity, tenderness on point pressure)

Benign presentations

• Traumatic onycholysis from nail cosmetics or occupational exposure — resolves with avoidance
• Idiopathic onycholysis in women — chronic but cosmetically manageable
• Mild psoriatic onycholysis — may respond to topical therapy

Warning signs

• Chronic unexplained onycholysis of a single nail — must rule out subungual squamous cell carcinoma
• Onycholysis with hemorrhagic streaks after starting a new medication — drug-induced, consider photo-onycholysis
• Multiple-nail onycholysis with systemic symptoms — evaluate for thyroid disease, systemic conditions
• Rapidly progressive onycholysis with subungual mass — consider tumor

Emergency presentations

• Acute painful subungual hemorrhage with onycholysis after trauma — evaluate for nail bed laceration, especially in children (may need nail plate removal for repair)
• Onycholysis with purulent discharge and fever — evaluate for deep infection

Professional documentation should include:

• Pattern: Distal, lateral, proximal, or semilunar
• Extent: Approximate percentage of nail plate detached; distance from free edge
• Border: Smooth, irregular, jagged; presence of oil-drop sign or spikes
• Color of onycholytic space: White, green, yellow-brown, hemorrhagic
• Associated nail changes: Pitting, ridging, subungual hyperkeratosis, splinter hemorrhages
• Number of nails: Specify which digits are affected
• Photography: With consent; document for comparison at follow-up

Example: "Distal onycholysis of the right ring fingernail, involving approximately 40% of the nail plate with an irregular, erythematous proximal border and oil-drop discoloration; subungual hyperkeratosis present; no pitting. Other nails normal. Psoriatic plaques on bilateral elbows."

• General measures for all onycholysis: Keep nails trimmed short (trim the detached portion); avoid trauma; keep nails dry (minimize wet work, wear gloves when washing); avoid contact irritants and nail cosmetics; protect hands from cold and wind
• Traumatic onycholysis: Remove causative factor; gentle nail care; the nail reattaches as it grows out (takes 3–6 months for fingernails, 6–12 months for toenails)
• Psoriatic onycholysis: Topical corticosteroids or calcipotriol applied to the hyponychium; in severe cases, systemic psoriasis therapy (biologics) improves nail disease
• Onychomycosis: Confirm with KOH/culture before treating; topical or systemic antifungal therapy depending on extent
• Secondary Pseudomonas infection: Trim the detached nail, keep dry, topical antiseptic (dilute acetic acid soaks); topical fluoroquinolone if persistent
• Drug-induced/photo-onycholysis: Discontinue the offending agent if possible; sun protection of nails if medication cannot be stopped
• Subungual tumor: Biopsy and appropriate surgical management
• Idiopathic onycholysis: Conservative management with nail care measures; may have a chronic, relapsing course

Key points for patient education:

• Nail separation is common and usually caused by everyday factors — trauma, irritants, nail cosmetics, or wet work
• Once the nail separates, it cannot reattach to the bed; you must wait for new, attached nail to grow forward (this takes months)
• Keeping the nail short and dry is the most important thing you can do to help the nail recover and prevent infection
• Avoid pushing debris or medication under the detached nail, as this can worsen the separation
• A green color suggests a harmless bacterial colonization (Pseudomonas) — it is cosmetically unappealing but treatable
• If the separation is spreading or affecting many nails, see your dermatologist to look for an underlying cause
• Always mention new medications to your doctor, especially antibiotics, if you notice nail changes after sun exposure