Epidermis

The epidermis is the thin outermost layer of skin, made up mostly of keratinocytes that migrate upward as they mature, plus the melanocytes that produce melanin. Its dead, flattened surface—the stratum corneum—is the body’s frontline barrier against water loss and infection.

For energy-based aesthetics, the epidermis is both a gateway and a liability. Treatments aimed at the dermis (RF tightening, hair lasers, non-ablative resurfacing) must pass through it without damaging it, which is why epidermal cooling matters. Treatments aimed at the surface (microdermabrasion, ablative resurfacing, chemical peels) work directly on it. And because the epidermis holds the skin’s melanin, its pigment level—captured by the Fitzpatrick scale—is what makes darker skin more vulnerable to surface burns.

Knowing whether a treatment targets the epidermis or must protect it clarifies how every device should be set up.