3.3 Nail Disorders & Diseases
Key Takeaways
- A nail disorder is a cosmetic or structural abnormality; a nail disease is a medical condition — nail technicians must never diagnose or treat diseases
- Any condition that is contagious, infectious, inflamed, swollen, or has open lesions requires refusing service and referring the client to a physician
- Onychomycosis (fungal infection), paronychia (bacterial infection of the nail fold), and Pseudomonas (green nail) are all contagious and require referral
- Cosmetic conditions like hangnails, mild leukonychia (white spots), and onychorrhexis (longitudinal ridges) can be addressed by a nail technician without referral
The Critical Distinction: Disorder vs. Disease
On the NIC theory exam and in professional practice, the distinction between a nail disorder and a nail disease is fundamental:
- A nail disorder is a cosmetic or structural abnormality of the nail unit that is not caused by a pathogen (bacteria, fungi, viruses). Examples: ridges, white spots, hangnails, brittle nails. A nail technician may cosmetically address many disorders.
- A nail disease is a medical condition caused by a pathogen or underlying health problem. Examples: fungal infections, bacterial infections, viral infections (warts, herpes). A nail technician must never diagnose or treat a disease. If a disease is suspected, the technician must refuse service and refer the client to a physician.
The Golden Rule
If a condition is contagious, infectious, inflamed, swollen, bleeding, or has open lesions, do NOT provide the service. Refer the client to a physician.
This rule overrides any client preference or desire for service. Providing a service on an infected nail can spread the infection, worsen the condition, and expose the technician and other clients to pathogens.
Comprehensive Reference Table
| Condition | Type | Signs & Symptoms | Contagious? | Action |
|---|---|---|---|---|
| Onychomycosis | Disease (fungal) | Thickened, yellowed, brittle, crumbling nail plate; white or yellow streaks; debris under the nail | Yes (contagious fungal infection) | Do NOT service; refer to physician |
| Paronychia | Disease (bacterial) | Redness, swelling, pus, pain around the nail fold; often at the cuticle area | Yes (bacterial infection) | Do NOT service; refer to physician |
| Onycholysis | Disorder | Separation of the nail plate from the nail bed; whitish discoloration of separated area | Not inherently contagious | May cosmetically address if not infected; avoid aggravating; refer if severe |
| Onychorrhexis | Disorder | Longitudinal ridges running from cuticle to free edge; brittle, splitting nails | No | May cosmetically address with gentle buffing and conditioning |
| Onychauxis | Disorder | Abnormally thick nail plate; may be caused by trauma, aging, or circulation issues | No | May cosmetically address by carefully thinning with a file; refer if caused by underlying disease |
| Beau's lines | Disorder | Horizontal depressions or grooves across the nail plate; caused by temporary disruption of matrix growth (illness, injury, stress) | No | May cosmetically address with gentle buffing; nail will grow out normally |
| Koilonychia | Disorder | Spoon-shaped nails that dip inward; may indicate iron deficiency | No | May cosmetically address; recommend physician evaluation if cause is unknown |
| Leukonychia | Disorder | White spots or white streaks on the nail plate; caused by minor trauma to the matrix | No | May cosmetically address; spots grow out with the nail |
| Pterygium | Disorder | Overgrown cuticle that attaches to the nail plate and stretches forward; skin grows over the nail | No | May cosmetically address with gentle cuticle care; do not force removal |
| Green nail (Pseudomonas) | Disease (bacterial) | Greenish discoloration under the nail plate; caused by Pseudomonas bacteria; often under artificial enhancements | Yes (bacterial infection) | Do NOT service; remove enhancement if present; refer to physician |
| Hangnail (agnail) | Disorder | Torn strip of skin at the side of the nail or cuticle; caused by dry skin or picking | No | May cosmetically address by carefully trimming with nippers; apply cuticle oil |
| Nail psoriasis | Disease (autoimmune) | Pitting, discoloration, thickening, onycholysis, oil-drop staining under the nail | Not contagious but is a medical condition | May provide cosmetic services if not inflamed or infected; refer for medical management |
| Warts (verrucae) | Disease (viral) | Rough, raised growths on the skin around or under the nail; caused by HPV | Yes (viral infection) | Do NOT service affected area; refer to physician |
| Tinea (ringworm) | Disease (fungal) | Red, itchy, scaly patches on the skin; can affect feet (tinea pedis / athlete's foot) | Yes (contagious fungal infection) | Do NOT service; refer to physician |
Key Conditions in Detail
Onychomycosis (Nail Fungus)
The most common nail disease a nail technician will encounter. Caused by dermatophyte fungi that invade the nail plate and bed. Signs include thickening, yellow-brown discoloration, crumbling, and debris under the nail. It is contagious — spores can spread to other nails, other clients, and surfaces. Never provide a service on a nail with suspected onychomycosis. Refer the client to a physician.
Paronychia
A bacterial infection of the tissue around the nail (the nail fold and cuticle area). It presents with redness, swelling, pain, and often pus. It can be acute (sudden onset) or chronic (long-lasting, often from repeated wetting). It is contagious. Refuse service and refer to a physician.
Pseudomonas (Green Nail Syndrome)
A bacterial infection caused by Pseudomonas aeruginosa. It produces a characteristic green, greenish-brown, or greenish-black discoloration under the nail plate. It often develops under artificial enhancements where moisture is trapped. It is contagious and requires removing the enhancement, discontinuing service, and referring to a physician. The green pigment is a byproduct of bacterial metabolism.
Onycholysis
The separation of the nail plate from the nail bed starting at the free edge and progressing toward the matrix. The separated area appears whitish because air enters the space. Causes include trauma, allergic reactions, prolonged moisture, and certain medications. Onycholysis itself is not contagious, but it can become infected. If there are no signs of infection, a nail technician may provide limited cosmetic services, but should avoid aggravating the separation.
Beau's Lines
Horizontal depressions across the nail plate caused by a temporary disruption in nail growth at the matrix. Common triggers include high fever, severe illness, surgery, emotional stress, or certain medications. The lines grow out with the nail. They are cosmetic and not contagious; gentle buffing can improve appearance.
Hangnail (Agnail)
A torn strip of skin at the side of the nail or cuticle. Caused by dry skin, picking, or minor trauma. Not contagious. A nail technician may carefully trim a hangnail with clean nippers and recommend cuticle oil to prevent recurrence. Never pull or tear a hangnail — this can cause tearing into living tissue and lead to infection.
Conditions a Nail Technician CAN Cosmetically Address
- Hangnails — carefully trim with clean nippers
- Leukonychia (white spots) — grow out naturally; cosmetically conceal if desired
- Onychorrhexis (ridges) — gentle buffing to smooth the surface
- Mild onychauxis (thick nails) — careful filing to thin the plate
- Beau's lines — gentle buffing; will grow out
- Pterygium — gentle cuticle care; do not force
- Dry, callused skin — moisturize and file (never cut with a blade)
Conditions That Require Refusal of Service and Referral
- Any contagious or infectious condition (fungal, bacterial, viral)
- Inflamed, swollen, or painful tissue
- Open wounds, cuts, or bleeding
- Suspicious moles, growths, or discoloration of unknown cause
- Severe or unexplained nail changes
Exam Traps
- Onychomycosis is contagious — always refuse service and refer.
- Pseudomonas (green nail) is a bacterial infection, not a stain — it requires medical referral, not more polish.
- Beau's lines are horizontal, not vertical — do not confuse with onychorrhexis (longitudinal ridges).
- Hangnails can be cosmetically trimmed — they are not contagious. But never pull or tear them.
- Nail psoriasis is not contagious but is a medical condition — cosmetic services may be provided if the area is not inflamed or infected, but refer for management.
A client presents with thickened, yellowed, crumbling nails with debris under the free edge. What condition is most likely, and what is the correct action?
Which of the following nail conditions can a nail technician cosmetically address without referring the client to a physician?
What causes Beau's lines, and how do they appear on the nail plate?
A client wearing artificial nail enhancements notices greenish discoloration developing under one nail. What is the correct professional response?