Overview of Skin Layers

The skin is composed of three primary layers: the epidermis, the dermis, and the subcutaneous fat (hypodermis). For aesthetic practice, the epidermis and dermis are the most clinically relevant.

The epidermis is the outermost layer and is itself made up of several sublayers. From deepest to most superficial, these include the stratum basale (basal cell layer), where new skin cells and melanocytes reside; the stratum spinosum, which provides structural strength; the stratum granulosum, where cells begin to flatten and release lipids; and the stratum corneum, the outermost barrier of dead cells embedded in a lipid matrix that protects against water loss and environmental damage.

The dermis sits beneath the epidermis and is divided into two regions. The papillary dermis is the thinner, upper portion containing fine collagen fibres, capillaries, and nerve endings close to the epidermis. The reticular dermis is the thicker, lower portion containing dense collagen bundles, elastin fibres, blood vessels, oil glands, sweat glands, and hair follicles — this is where most structural support originates.

Below the dermis lies the subcutaneous fat layer (hypodermis), which contains adipose tissue, larger blood vessels, and connective tissue. While not directly targeted by most surface treatments, it plays a role in volume, insulation, and cushioning.

Understanding which layer — and which sublayer — you are affecting is critical. Treating too superficially may limit results, while treating too deeply or aggressively may cause damage. Effective treatment requires alignment between the condition and the depth of intervention.