Skin Sciences and Skin Analysis
Structure and function
Build a mental map of the epidermis: stratum corneum (barrier), granulosum, spinosum, basale (where keratinocytes divide and melanocytes sit). Below it, the dermis holds collagen, elastin, sebaceous and sweat glands, hair follicles, and vessels; then subcutaneous fat. Know the barrier's chemistry: the acid mantle sits near pH 4.5–5.5, formed by sebum and sweat, and it controls water loss and bacterial growth. Skin functions to protect, sense, secrete, excrete, absorb, regulate temperature, and synthesize vitamin D.
Classification
Skin types - normal, dry, oily, combination, sensitive - are genetic and do not change. Skin conditions (dehydration, acne, pigmentation, aging, rosacea-like redness) vary with health, season, and habits. Fitzpatrick phototypes I–VI predict sun response and treatment risk. UVB causes burning; UVA drives aging and pigmentation.
Lesions
Learn primary versus secondary. Primary: macule, papule, pustule, vesicle, bulla (over 1 cm), wheal, nodule, cyst, tumor. Secondary: crust, scale, scar, excoriation, fissure, ulcer, atrophy. Estheticians describe and refer; they do not diagnose.
Analysis tools
Visual inspection, palpation, magnifying lamp, and Wood's lamp. Under Wood's lamp: blue-white = normal, orange/yellow = oily, violet/purple = dehydration, brown = pigmentation, coral-red = possible bacterial involvement, yellow-green fluorescence = fungal suspicion (refer).
Traps
Questions swap macule and papule, or vesicle and bulla. They also claim a topical product changes skin type. Suspicious, changing, or undiagnosed lesions are never treated.
Rule of thumb
Describe what you see, name the condition, then check it against your scope: if it is a lesion you cannot identify with confidence, treat around it and refer.