Subcutaneous tissue (hypodermis): the fat layer under the skin

Subcutaneous tissue, or hypodermis, is the layer just below the dermis. It is made mainly of adipocytes (fat cells) organized by septa of connective tissue, with vessels, nerves and lymphatics running between them. In body skin, it works as a cushion, a thermal insulator and an energy reserve. In the face, it also helps define contour and volume.

What is it like in the face?

In the face, subcutaneous fat is not a uniform layer: it is divided into compartments, separated by septa and anchored by cutaneous ligaments. These compartments, described in superficial compartments of the face, age differently. In some places the fat diminishes, in others it descends, and the difference between them creates folds and areas of shadow.

Below the subcutaneous tissue comes the SMAS, the musculoaponeurotic layer, which serves as a reference for the layers of the face. This set helps explain why the same product behaves differently in each region and in each patient.

What changes with age and weight?

• Over time, part of the facial fat loses volume and part shifts downward.
• Rapid weight loss, including with weight-loss medications, reduces facial fat and can accentuate folds and laxity.
• Weight gain increases volume, but does not on its own reverse established ptosis or laxity.
• The skin over the fat also thins, and the combination of the two changes the appearance.

Why does this matter in harmonization?

The thickness of the subcutaneous tissue influences how a filler looks and feels, how visible a nodule or irregularity is, and how a biostimulator or thread settles. In thin skin, the effect of a superficial plane tends to be more evident, and mistakes show more. In thicker skin, the reading is different. These choices belong to the qualified professional, according to the rules of their professional board, and are not a topic for public protocol.

Clinical attention

The subcutaneous tissue of the face contains small and medium-caliber vessels. In injectable procedures, vascular anatomy, the patient's history and hyaluronidase on hand (when hyaluronic acid is used) are part of safety. Bruising and swelling are expected to varying degrees and are linked to the vascularization of this layer.

In Harmy

Harmy's projection works with the outer appearance of the front photo and cannot see layers. It shows an illustration of the marked volume, without representing the thickness of fat, skin or the plane of application.

Also called: hypodermis, subcutaneous layer.