Skin and Nail Care
This domain covers skin structure and lesions, contagious conditions you must refuse, and nail anatomy and disorders.
Skin layers
Epidermis (outermost, with the basal layer producing new cells that keratinize as they rise), dermis (collagen, elastin, nerves, glands, follicles), and subcutaneous tissue (fat, insulation). Skin types: normal, dry, oily, combination, sensitive.
Lesions
Primary - macule (flat color change), papule (small raised solid), vesicle (small blister, clear fluid), pustule (pus-filled), bulla (large blister), wheal (raised, itchy, hive-like). Secondary - crust, scale, fissure, scar, ulcer, excoriation.
Contagious: refuse and refer
Impetigo, tinea (ringworm), herpes simplex, warts, molluscum contagiosum, pediculosis, and scabies. Do not shave, massage, or apply product over them.
Nails
Nail plate, nail bed, matrix (where growth occurs), cuticle, lunula, free edge. Nails grow roughly 3 mm per month. Disorders to recognize: paronychia (red, swollen, painful nail fold, often infectious - refer), onychosis (general deformity), onychorrhexis (brittle, split), leukonychia (white spots), and bruised nail. Never cut living tissue or aggressively push back the cuticle.
Worked example
A client's nail fold is red, swollen, and draining pus. That is paronychia, likely bacterial. Do not perform the service; refer to a physician. Filing nearby healthy nails does not make the service acceptable.
Traps that cost marks
Calling a wheal a vesicle, treating a pigmented lesion as something to work across, and assuming the cuticle is dead tissue to be removed entirely.