7.3 Nail Structure, Growth, Diseases & Disorders

7.3 Nail Structure, Growth, Diseases & Disorders

Quick Answer: The nail unit includes nail plate, nail bed, matrix, cuticle, eponychium, hyponychium, free edge, and lunula. The matrix generates the plate; healthy growth is often taught as about 1/8 inch (≈3 mm) per month for fingernails (toenails slower). Recognize onychomycosis, paronychia, onycholysis, ingrown nails, and bruises — and know contraindications for manicure, pedicure, and enhancements. This content supports Anatomy & Physiology (27%) and Nail Care & Services (7%) on the Ohio Cosmetology Theory TIP.

Nails are specialized appendages of the skin — hard plates of keratin that protect fingertips and toes and aid fine motor tasks. Ohio theory expects structural accuracy plus service judgment: a pretty enhancement on an infected nail is both an exam wrong answer and a real-world license risk.

Anatomy of the Nail Unit

Critical distinctions for exams:

• Cuticle vs. eponychium — Cuticle is the dead tissue adhered to the plate; eponychium is living skin. Aggressive cutting of living tissue invites paronychia and blood exposure.
• Plate vs. bed — The plate is hard keratin; the bed is living tissue with nerves and vessels. Separating plate from bed (onycholysis) is abnormal.
• Matrix damage — A crush injury, aggressive “deep” work under the proximal fold, or infection involving the matrix can leave ridges, pits, or permanent deformity long after the appointment.

How Nails Grow

Nail plate growth is continuous in healthy individuals:

• Fingernails — Commonly taught average growth is about 1/8 inch (approximately 3–3.5 mm) per month. Full replacement of a fingernail can take roughly 4–6 months.
• Toenails — Grow more slowly; full replacement may take 12–18 months (ranges vary by individual).

Factors that influence growth and quality (recognition level):

• Age — Growth often slows with age.
• Season and circulation — Warmer months and better peripheral blood flow may support faster growth.
• Nutrition and general health — Severe illness, chemotherapy, and some systemic conditions alter growth rate or produce Beau’s lines/ridges.
• Trauma — Single injuries can cause temporary shedding or deformity.

Cosmetologists cannot force dramatically faster healthy growth with a single product claim. You can protect the free edge, avoid over-filing the plate thin, maintain gentle cuticle care, and refer systemic concerns to physicians.

Healthy Nail Signs vs. Warning Signs

Healthy nails are generally firm but flexible enough not to shatter, relatively smooth, evenly pink under the plate (from the bed’s blood supply), and free of pain, pus, or foul odor.

Warning signs include pain, swelling, redness, heat, pus, green-black discoloration under enhancements, lifting, thickening with crumbly texture, foul smell, or client-reported fever with local infection — all trigger stop service / refer thinking.

High-Yield Diseases and Disorders

Onychomycosis (Tinea Unguium) — Fungal Nail Infection

Onychomycosis is a fungal infection of the nail plate/bed. Appearance may include thickening, discoloration (yellow/brown/white), brittleness, and debris under the plate. It is contagious in the sense of fungal transmission risk in multi-client settings when implements and pedicure equipment are poorly disinfected.

Salon action: Do not perform pedicure services that file aggressively into infected debris as “treatment,” do not apply enhancements over active infection, and refer to a physician/podiatrist. Follow Ohio-aligned disinfection of implements and pedicure equipment rigorously for every client to prevent spread.

Paronychia

Paronychia is bacterial (sometimes fungal/yeast-related) infection of the tissue surrounding the nail, often after trauma to the eponychium/cuticle area. Signs: redness, swelling, pain, possible pus.

Salon action: Refuse service on the affected digit/foot area; do not lance or squeeze; refer. Teach prevention by avoiding cutting living tissue and keeping tools disinfected.

Onycholysis

Onycholysis is separation of the nail plate from the nail bed, often starting at the free edge and progressing proximally. Causes include trauma, aggressive filing/lifting of enhancements, chemical irritation, and medical conditions.

Salon action: Avoid prying, aggressive scraping under the plate, or “sealing” lift with more product over an unclean separation. Mild mechanical separation from length may improve with careful shortening; infection, pain, or progressive unexplained lifting needs referral. Do not force enhancements onto chronically lifting plates without addressing cause.

Ingrown Nails (Onychocryptosis)

Ingrown nails occur when the plate grows into the surrounding soft tissue, causing pain, redness, and possible infection — especially on toes.

Salon action: Do not dig deep spurs out of inflamed tissue as a surgical procedure. Mild, non-infected cases may allow careful filing of the free edge per training; inflamed, infected, or diabetic-foot-risk clients need medical referral. Pedicure contraindication is strong when infection is present.

Bruises and Hematoma (Including “Blue” Nails from Trauma)

Trauma can cause subungual hematoma — blood under the plate — with pain and dark discoloration. Cosmetologists may see this after crush injuries or tight shoes.

Salon action: Do not drill or relieve pressure under the plate (medical procedure). Avoid further trauma; postpone enhancements if the plate is unstable; refer for significant pain or pressure.

Other Terms Worth Knowing

• Onychophagy — Nail biting; increases infection risk and uneven free edges.
• Onychorrhexis — Split or brittle nails with lengthwise ridges.
• Beau’s lines — Transverse depressions from temporary matrix interruption.
• Pterygium (nail context) — Abnormal forward growth of eponychium/cuticle tissue onto the plate; do not force-tear living tissue.
• Pseudomonas-related green discoloration under enhancements — Often linked to moisture trapped under lift; remove product carefully per training, do not ignore as “just stain,” and refer if infection is suspected.

Contraindications for Manicure, Pedicure, and Enhancements

Refuse or significantly modify services when you find:

1. Suspected fungal infection (onychomycosis) of nails being treated.
2. Paronychia or other active periungual infection.
3. Open wounds, ulcerations, or bleeding around nails/feet.
4. Severe onycholysis with debris, odor, or pain.
5. Infected ingrown nails.
6. Unexplained dystrophy, sudden color change without trauma history, or client medical advice against service (including some high-risk diabetes/neuropathy foot cases — medical clearance culture is wise).
7. Allergic reaction history to monomers/resins for the planned enhancement system.

Enhancement-specific caution: Acrylic, gel, and tip systems over diseased nails can trap moisture and pathogens, worsen fungal problems, and conceal progression. Healthy nail plate and surrounding skin are prerequisites — not optional aesthetics.

Infection control reminder: Pedicure bowls, bits, clippers, and files must meet cleaning/disinfection standards between clients. Single-use items stay single-use. Ohio sanitation expectations (OAC 4713-aligned practice) are inseparable from nail disorder prevention.

Connecting Nail A&P to the Full Exam

• A&P 27% — Structure names, matrix function, growth concepts.
• Nail Care 7% — Service procedures assume you already know when not to proceed.
• Infection Control 24% — Fungal and bacterial risks around nail services are classic cross-domain items.

Study Strategy

• Sketch a nail unit and label eight structures without notes.
• Write one sentence: “The matrix does X; damage causes Y.”
• Build a three-column card for each disorder: definition | contagious/infectious risk | salon action.
• Quiz yourself: “Can I put an enhancement on this nail today — yes/no/why?”

With skin structure (7.1), skin disorders (7.2), and nail structure/disorders (7.3), you hold a major block of Ohio theory A&P. Next chapters extend the same recognition-and-safety habits into hair structure and scalp disorders.