6.1 Noninfectious Nail Disorders

Recognize, do not diagnose

Quick Answer: A disorder is a noninfectious change in the nail unit. It is usually not contagious, but it can still be a stop-the-enhancement finding. You describe signs (what you see) and symptoms the client reports (pain, tenderness). You do not name a medical diagnosis or sell a treatment. 18VAC41-20-270 F 2 allows an artificial nail only on a healthy natural nail.

NIC Nail Technology theory Domain 2 (Anatomy and Physiology, 15%, CIB effective September 1, 2025) includes recognizing signs, symptoms, and causes of disorders of the nails. Virginia’s 150-hour curriculum budgets 10 hours to diseases and disorders of the nail (18VAC41-20-210 F). Those hours are not a mini-dermatology degree. They train you to see Beau's lines, leukonychia, onycholysis, and a dark streak, then to choose a safe service, a modified natural-nail service, or a refusal and referral.

A disorder is generally not contagious. A disease (Section 6.2) involves a pathogen or an infectious process and is a stop-and-refer event. Do not mix the two. Onycholysis can be a trauma disorder or a sign sitting next to fungus or psoriasis. If you cannot tell, you do not guess with a file. You postpone the requested service and refer.

You are not a physician. Cosmetologists and nail technicians in Virginia recognize abnormal findings, refuse unsafe services, and refer. Covering a problem plate with acrylic is not concealment; it is a sanitation and client-health failure under 18VAC41-20-270 A 4 and F 2.

Growth interruptions and surface ridges

Beau's lines are horizontal depressions or furrows that run across the plate, from sidewall to sidewall. They form when the matrix briefly stops producing nail. Causes include high fever, systemic illness, chemotherapy, zinc disruption, or injury at the base of the nail. The line then grows forward with the plate. They are not contagious. Do not file the furrow away; you will thin an already interrupted plate. A gentle natural manicure is acceptable if the surrounding skin is intact and there is no pain. Enhancements are not appropriate while the plate is grooved and fragile.

Corrugations are wavy ridges, often horizontal, from injury or uneven matrix output. Ridges in everyday salon language are usually lengthwise (longitudinal) lines that become more visible with age as the matrix produces keratin less evenly. Neither finding is contagious. Light buffing of high spots is a service adaptation only when the plate is thick enough to spare. Filing ridges “flat” on a thin plate creates onycholysis and a portal of entry. If the client wants a glass-smooth surface, that is a consultation moment, not a license to sand living nail down to the bed.

Thin, soft, and spoon-shaped plates

Eggshell nails are noticeably thin, white, and flexible, and they often curve over the free edge. Textbook language also uses onychomalacia for softening of the nail. Causes include internal illness, medication, diet, heredity, and nervous-system stress on growth. The plate can bend under ordinary clipper pressure. Not contagious. This is a classic do-not-enhance nail. Primer, monomer, and e-file heat on a paper-thin plate injure the bed. Virginia’s healthy-natural-nail rule is the service answer: no artificial nail. Offer a short, careful natural service; recommend an oil manicure for brittleness (the NIC sample use of oil manicures), and send persistent or painful change to a physician.

Koilonychia is the spoon nail: the plate is concave and can hold a drop of water. Causes include iron-deficiency patterns, occupational contact with oils and solvents, and hereditary shape. The plate is often thin and soft. Not contagious. Do not force it flat with product. No sculpted nail on a spooned, weakened plate. If the client also reports fatigue or new onset in adulthood, that is referral territory; you are seeing a sign, not treating anemia.

Thickness and overcurvature

Onychauxis is hypertrophy—a thickened plate—without the hooked ram’s-horn curve. Trauma, age, and footwear pressure are common causes, especially on toenails. Not contagious by itself. A painless, mildly thick toenail with intact skin may be shortened carefully with a clipper designed for thick nails. Aggressive grinding of living nail with a motorized bit is not a Virginia nail-technician move: 18VAC41-20-270 F 3 limits a nail drill to the artificial nail surface only. Pain, odor, debris, or crumbling thickness is no longer “just onychauxis”—treat it as a possible disease and stop.

Onychogryposis is the ram’s horn nail: opaque, claw-like, thickened, and curved, often the great toenail in older clients. Neglect, trauma, and long-term pressure contribute. Not contagious, but the distorted plate can hide debris and injury. Do not try to “normalize” it with a salon e-file. Refer for medical care. A salon pedicure on a ram’s-horn nail that you cannot safely reduce is a refusal, not a challenge.

Pincer nails (also called trumpet nails) show transverse overcurvature: the side edges roll inward and can pinch the bed into a tube. Heredity, ill-fitting shoes, and trauma are causes. The client may report a tight, squeezing pain. Not contagious. Do not pry the edges open or pack product under the rolled walls. If the nail is tender, ingrown, or red at the fold, stop and refer. If it is painless and the skin is intact, a conservative trim of the free edge only—never a deep sidewall excavation—is the outer limit of a cosmetic service.

Plicatured nails are folded nails, often at one or both sides, and they are a setup for ingrown nails. Inherited curvature and tight shoes matter. Not contagious. File or clip only what you can see of the free edge. If the fold is already red, draining, or painful, that is an infected ingrown—a disease-level contraindication (Section 6.4), not a disorder you “work around.”

Habits, splits, and living skin at the sidewall

Onychophagy is nail biting. Plates are short, ragged, and uneven; the free edge may be gone. Surrounding skin is often chewed. Not contagious, but broken skin is a portal of entry. If tissue is intact, a gentle natural service and habit discussion are appropriate. If the skin is raw, bleeding, or obviously inflamed, stop. Bitten, thinned plates are not healthy natural nails for tips, acrylic, gel, or dip (270 F 2).

Onychorrhexis is split or brittle nails with lengthwise splitting and dry, rigid keratin. Harsh solvents, repeated water-and-dry cycles, injury, aging, and untreated dryness (anhydrous conditions, Section 6.3) are causes. Not contagious. This is the disorder for which NIC highlights oil manicures: oil supports flexibility in a brittle plate. Do not soak until the plate is waterlogged and then file the splits wider. No enhancement on a peeling, splitting plate.

Hangnails and agnail are the same finding: a strip of living skin beside the nail splits and peels. Dryness, cold, and cutting living tissue cause them. Not contagious unless the split becomes infected. You may carefully trim the dry, non-living tag with a clean nipper if the skin is not red. You may not cut into living, attached skin. Redness, swelling, pus, or throbbing means the hangnail has become a paronychia problem—leave Section 6.1 and refuse service.

Color, blood, and pigment you must not ignore

Leukonychia is white spots or streaks in the plate. The salon cause is almost always injury to the matrix or plate—a slammed finger, aggressive pusher, or heavy filing—not a calcium deficiency. That calcium story is an exam trap. Not contagious. Service is acceptable on an otherwise healthy nail. Do not drill the white spot; it will grow out.

Melanonychia is a brown or black longitudinal band of melanin in the plate. Even, stable bands are more common in darker skin phototypes. The finding you must not normalize is a sudden dark streak, a band that widens, irregular color, pigment that spills onto the proximal or lateral fold, or a streak in a single light-skinned nail with no history. Those are refer-now signs for possible melanoma or another physician-level pigmented lesion. Do not buff pigment. Do not apply opaque gel “so it looks better.” Nail technicians do not decide that a streak is “just ethnic pigment” when the history is new.

A bruised nail is pooled blood under the plate after known trauma: red-purple, then black, then growing forward. Splinter hemorrhages are thin longitudinal brown-red lines from ruptured capillaries in the bed. Known, recent trauma with an otherwise intact fold: document the story, avoid trapping blood under an enhancement, and consider postponing product until the plate is assessed. Unexplained bruising or splinters—especially several nails, no injury, or a new dark line the client did not notice until you pointed it out—refer. Unexplained blood-colored pigment is not a French-manicure problem.

Attachment failures: onycholysis, onychomadesis, pterygium

Onycholysis is separation of the plate from the bed, usually starting at the free edge and moving back. You see a white or yellowish air gap. Causes include trauma, over-filing, product allergy, aggressive lifting of the hyponychium, psoriasis, and fungal disease. The separation itself is not “a fungus,” but fungus loves the gap. Do not apply enhancements on a separated nail. Product in that space is a moisture chamber for Pseudomonas (Section 6.2). If the gap is clean, small, and clearly traumatic, you may discuss a natural-nail trim and referral or postponement—you still do not glue it down with acrylic. If there is odor, debris, thickness, or pain, treat it as disease-associated and stop.

Onychomadesis is shedding of the plate that begins at the proximal end (near the matrix) so the nail detaches and falls. Severe illness, high fever, trauma, and some drug reactions interrupt the matrix hard enough that a cleavage plane forms. Not contagious as a disorder. Do not service the loosening nail. Do not clip the remaining plate off as a “cleanup.” Protect the exposed bed from salon product and refer.

Pterygium is abnormal stretching of skin onto the nail plate. Dorsal pterygium grows from the eponychium; ventral pterygium grows from the hyponychium. Scarring, burns, lichen planus, and severe injury are causes. Not contagious. Do not push pterygium. Do not cut it. A cuticle pusher on true pterygium tears living tissue and can permanently distort the unit. This is a refer finding, not an “extra cuticle” finding.

Service-or-stop table for noninfectious disorders

Exam traps for 6.1

• White spots are leukonychia from injury, not “add calcium.”
• Green-yellow color is not a disorder in this list; it is Pseudomonas (next section).
• A disorder can still be a contraindication for enhancements. “Not contagious” is not the same as “healthy enough for acrylic.”
• Pterygium is not ordinary cuticle. Ordinary eponychium can be gently eased on a healthy nail; pterygium cannot.
• You do not treat koilonychia or Beau's lines. You recognize them and choose a safe cosmetic limit.