Hair and Skin Science
Core concepts
Know the anatomy of the hair follicle - bulb, papilla, matrix, root sheaths, sebaceous gland, arrector pili - and the three growth phases: anagen (active growth), catagen (transition), telogen (resting). The germinative cells that must be affected for lasting results sit near the bulb/papilla region, which is why insertion depth and probe placement matter. Understand hair types (vellus vs. terminal), regional variation, and how hormones, age, genetics, and medication shift growth patterns.
Skin science covers the epidermis and dermis, the barrier function, and how skin type and condition (dry, oily, sensitive, Fitzpatrick phototype) influence tolerance and aftercare. Recognize common conditions you may see - folliculitis, hyperpigmentation, pseudofolliculitis - and know which findings call for referral rather than treatment.
Traps to watch
Questions blur growth phases or imply all hairs are in the same phase at once. Watch for confusion between vellus and terminal hair, and between normal post-treatment redness and a true adverse reaction. Fitzpatrick typing questions reward matching aftercare/sun-protection advice to the client's risk of pigment change.
Worked example / rule of thumb
A client with darker skin worries about dark spots after treatment. Explain that melanin-rich skin carries higher risk of post-inflammatory hyperpigmentation, so you will use conservative settings, test tolerance, and emphasize sun protection. Rule of thumb: treat the skin you see and the hair you can reach - depth and phase together.
Study focus
Be able to label a follicle diagram from memory and match each growth phase to its clinical implication.