My fingernails feel like they are separating from the nail bed (onycholysis); what are the possible causes and how should I be evaluated and treated?

Onycholysis: Immediate Management and Diagnostic Workup

Trim the separated nail plate back to where it remains firmly attached to the nail bed—this is the single most important intervention to prevent chronic, irreversible nail bed changes. 1

Immediate Nail Management

The detached portion of your nail has lost its transparency and become opaque, creating a space where debris accumulates and secondary infection can develop. 1 Leaving the separated nail in place leads to chronic onycholysis with irreversible nail bed keratinization and persistent subungual hyperkeratosis. 1, 2

Proper Trimming Technique

• Cut nails straight across, not too short, ensuring they remain at the point of attachment 1
• Avoid cutting into the attached nail, which could extend the separation 1
• Continue regular trimming as the nail grows until the plate reattaches 1

Identify the Underlying Cause

Onycholysis has distinct etiologies depending on whether fingernails or toenails are affected:

Fingernail Onycholysis (Most Common Causes)

Trauma and occupational exposure account for the majority of fingernail onycholysis in women, often related to manicuring, occupational moisture exposure, or self-induced behavior. 3

Key diagnostic features to examine:

• Soft, friable texture with thickening and discoloration → strongly suggests fungal (dermatophyte) infection 4
• Swollen, erythematous cuticles (paronychia) with occupational wet work → points toward Candida infection, which starts proximally unlike dermatophytes that begin distally 4
• Nail pitting or multiple nails involved with skin plaques → suggests psoriasis 4
• Recent medication changes → phototoxic drugs (tetracyclines, fluoroquinolones, NSAIDs) or chemotherapy agents can cause onycholysis 5
• Unexplained fever with heart murmur → consider endocarditis 5

Toenail Onycholysis

Mechanical pressure from closed shoes during walking is the primary cause, particularly in patients with flat feet producing asymmetric gait. 3

Essential Diagnostic Testing

Do not assume fungal infection without laboratory confirmation—50% of dystrophic nails are non-fungal. 4

• Obtain mycological confirmation before starting antifungal therapy: potassium hydroxide (KOH) preparation with microscopy as first-line screening, followed by fungal culture on Sabouraud's glucose agar incubated for at least 3 weeks 4
• Collect subungual debris from the most proximal part of the infection using a dental scraper, as dermatophyte infections primarily affect the nail bed 4
• Check thyroid function and complete blood count if no obvious trauma or psoriasis is present, as onycholysis can indicate hyperthyroidism or anemia 5, 4
• Obtain bacterial cultures if signs of infection develop (occurs in up to 25% of cases), and initiate antibiotics with anti-staphylococcus aureus coverage 1

Daily Management Protocol

Drying and Protection

• Dry the onycholytic area with a hair dryer after any water exposure—all colonizing organisms are moisture-loving and perish in a dry environment 3
• Apply topical emollients daily to periungual folds, matrix, and nail plate 1, 2
• Use protective nail lacquers to limit water loss from the nail plate 1, 2

Skin Irritation Management

• Apply high-potency topical corticosteroid ointment twice daily to inflamed nail folds 1
• Use topical petrolatum around the nails for lubricant and smoothing effects 1
• Apply hypoallergenic moisturizing creams once daily and clean with pH5 neutral bath formulations 1

Strict Avoidance Measures

• No prolonged soaking in water 1, 2
• No exposure to solvents or harsh chemicals 1, 2
• No manipulation of cuticles or nail biting 1, 2
• No use of fingernails as tools 2
• Wear gloves while cleaning to prevent further irritation 1, 2

When to Escalate Treatment

Partial or total nail avulsion is required if painful hematoma, subungual abscess, or infection develops despite conservative management. 1, 2 Inadequate cleaning and debridement of the nail bed during removal causes complications, so this should be performed by an experienced clinician. 2

Critical Pitfall

The most common cause of treatment failure is incorrect diagnosis based solely on clinical grounds without laboratory confirmation. 4 Candida albicans is frequently recovered from the onycholytic space in women due to proximity of fingers to the vaginal and gastrointestinal tract, but treating Candida does not improve fingernail onycholysis—it is a colonizer, not the cause. 3 The longer onycholysis has been present, the less likely it is to resolve, making early aggressive management essential. 6