Skin aging is a natural part of life. Understanding how skin ages naturally is key to knowing how to properly care for it.
Marisa Plescia
Vice President, Society of Cosmetic Chemists; Founder, FemChem Beauty
The skin is the body’s largest organ and plays a vital role. Its primary function is to act as a protective barrier, shielding the body from environmental factors like heat, cold, harmful UV rays, and invading bacteria. In addition to protection, the skin also serves as a sensory organ, allowing us to detect temperature, pressure, pain, and itch. The skin can generally be divided into three main layers:
- Epidermis: This is the outer part of the skin and provides a protective barrier against the external environment. It contains skin cells, pigment, and proteins, such as keratin. The epidermis plays a crucial role in skin hydration.
- Dermis: The middle layer of the skin accounts for 90% of the skin’s thickness. The dermis is composed of skin cells, blood vessels, nerves, hair follicles, and oil glands. The dermis also contains the vital skin proteins collagen and elastin. Collagen provides strength and structure to the skin, while elastin helps keep skin flexible and helps skin regain its shape after being stretched.
- Hypodermis/subcutaneous: The inner/deepest layer of the skin is primarily composed of fat cells, connective tissue, and blood vessels. This layer helps provide insulation, cushioning/protection of inner organs and tissue, and anchoring of the upper layers of the skin to the muscles.
Signs of skin aging
Changes in the skin are some of the most noticeable indicators of aging. The evolution of our skin is shaped by a complex interplay of genetics and the biology of time, lifestyle choices, and environmental influences. These factors are often categorized as two types of skin aging: intrinsic aging and extrinsic aging. Intrinsic aging, otherwise known as chronological aging, is the natural, time-dependent deterioration of skin function and structure that occurs as a result of biological processes. Extrinsic aging refers to the visible signs of skin aging that are caused by external factors, such as sun exposure, diet, and pollution.
The most common visible signs of skin aging include:
- Fine lines and wrinkles
- Sagging skin and loss of skin elasticity and volume
- Uneven skin tone and hyperpigmentation
- Skin dryness and dehydration
- Dullness and loss of radiance
- Thinning skin and fragility
- Enlarged pores and skin redness
- Uneven skin texture
While intrinsic aging accounts for only about 20% of overall skin aging, with the remaining 80% driven by external factors, understanding its role is essential to grasp how our skin naturally changes over time. Despite its smaller contribution, intrinsic aging plays a critical role in the fundamental, time-dependent structural and functional changes of the skin.
Intrinsic aging influences
At the core of intrinsic skin aging lies genetics. Our DNA fundamentally determines how skin functions and changes throughout life. Numerous genes are involved in regulating skin aging, and several DNA-driven biological mechanisms influence the skin, leading to the effects of skin aging. These include:
- Telomere Shortening: Every time a cell divides, the protective caps on the ends of chromosomes (telomeres) get shorter. When they become too short, the cells can no longer divide properly or function effectively, leading to dysfunctional and reduced healthy skin cells.
- Decreased Mitochondrial Function: Mitochondria are the powerhouses of the cell, providing energy for cellular activities. As you age, their function declines, reducing the skin’s ability to repair and regenerate.
- Oxidative Stress: The body generates free radicals during normal metabolism and cellular processes. Over time, accumulated oxidative stress damages DNA, proteins, and lipids in the skin.
- Hormonal Changes: Shifts in hormones throughout life can significantly affect skin cells and their processes.
As a result of these changing key biological mechanisms, several important changes in the skin are triggered:
- The overall integrity of the essential skin proteins of collagen, elastin, and keratin is compromised and decreases. A process called glycation — the binding of sugars to collagen and elastin — increases as you age, which weakens collagen and elastin. Additionally, decreased estrogen, which happens naturally as you mature, can also lead to a decline in collagen. Therefore, skin becomes less firm, strong, and elastic. This leads to fine lines, wrinkles, and sagging.
- In more youthful skin, new cells can replace old cells at a more rapid pace. This helps keep the skin complexion glowing. With telomere shortening and hormonal changes, the process of cell turnover slows dramatically. This can lead to a dull, rough, or uneven skin tone.
- Sebaceous (oil) gland activity naturally declines with age, primarily due to the hormonal changes and the reduction in cell turnover. While the glands may become larger (i.e., enlarged pores), their ability to produce sebum, which lubricates the skin, diminishes. This leads to drier skin in older individuals. Additionally, the synthesis of natural moisturizing factors within the skin decreases, making it harder for the skin to hold onto water. Therefore, more mature skin can be drier, which leads to skin flaking and a rougher texture.
- With all the changes in skin proteins, both the epidermis and the dermis thin over time. The dermal epidermal junction, also called the DEJ, which is the boundary between the epidermis and dermis, also flattens and weakens. This makes skin more fragile, more prone to injury, and slower to heal. The subcutaneous layer also shrinks with age, and the amount of fat lessens, especially around the cheeks, eyes, and hands. This can lead to a hollowed appearance.
- While uneven pigmentation is more commonly associated with extrinsic aging, especially sun damage, intrinsic aging can also cause minor changes in skin color. Melanocyte (cells that produce pigment) activity and structure changes, which can lead to paler skin, but also uneven skin tone.
Intrinsic aging is a gradual, genetically programmed process that shapes how our skin changes as we age. From declining collagen production to slower cell turnover and reduced elasticity, these internal shifts reflect the natural rhythm of biological aging. Although extrinsic factors like sun exposure may accelerate visible signs of aging, understanding the foundational role of intrinsic aging offers valuable insight into the skin’s long-term evolution. While we can’t stop skin aging, understanding its role gives us a clearer picture of how our skin evolves and empowers us to care for it more effectively as we age.
