What it is
The hypodermis, also known as the subcutaneous layer, is the deepest layer of the skin. It lies beneath the dermis and serves as a cushion between the skin and underlying muscles and bones. This layer is made up primarily of fat cells (adipocytes), connective tissue and larger blood vessels and nerves.
The hypodermis acts as an energy reserve, insulates the body to help regulate temperature and provides shock absorption to protect internal organs. Its fat content also influences the shape and fullness of the skin. In aesthetic treatments, the volume and condition of the hypodermis can significantly impact how youthful or contoured the face and body appear.
The hypodermis in dermatology
While the hypodermis is not directly targeted by most topical skincare products, it is important in overall skin health and ageing. With age, the fat in the hypodermis can become unevenly distributed or decrease in volume, contributing to hollowness, sagging and changes in facial contours. This is a natural part of the ageing process but may be accelerated by sun exposure, smoking and extreme weight loss.
In clinical aesthetics, the hypodermis is often the focus of injectable treatments. Dermal fillers, typically made of hyaluronic acid, are used to restore volume lost from this layer. Skin boosters and biostimulators are also injected into or near the hypodermis to improve hydration, stimulate collagen and enhance skin elasticity. Polynucleotide injections, for example, may also involve this layer.
Although you cannot reach the hypodermis with standard skincare, maintaining a healthy lifestyle supports its function. Stable weight, balanced nutrition and sun protection all help preserve the structural integrity of this layer over time. Exercise and hydration can also improve circulation, which benefits the entirety of the skin.