Plain-language definitions of the terms behind hand aging and biological age estimation. Each entry is a self-contained answer to "what is this," written to be quoted directly.
Biological hand age is an estimate of how old your hands appear based on visible signs of aging, rather than your actual chronological age. It is derived from skin texture, sun damage, collagen loss, vein prominence, and nail condition. Because hands are rarely protected the way the face is, biological hand age often exceeds chronological age.
Chronological age is the number of years a person has been alive. It is the baseline that biological hand age is compared against. A gap between the two indicates that the hands are aging faster or slower than expected for that person's years.
Dorsal hand skin is the skin on the back of the hand, the surface most exposed to sun and most commonly assessed for aging. It is roughly 30% thinner than facial skin and has less underlying fat, so structural aging shows there sooner and more visibly.
Solar lentigines, commonly called sun spots or age spots, are flat brown patches caused by cumulative ultraviolet exposure. On the hands they are one of the clearest markers of photoaging and a major contributor to a hand looking older than its chronological age.
Collagen loss is the gradual decline of the structural protein that keeps skin firm and plump. In the hands it produces crepey texture, fine lines, and a thinner appearance. It is driven by both natural aging and UV exposure, and it responds to retinoids over 60 to 90 days.
Vein and tendon prominence refers to how visibly the veins and tendons stand out on the back of the hand. It increases as the fat layer beneath the skin thins with age, rather than the veins themselves enlarging. Hydration and firming products soften its appearance but do not reverse volume loss.
Photoaging is skin aging caused by ultraviolet light rather than the passage of time. It is the primary driver of hand aging and produces sun spots, rough texture, and collagen breakdown. Because it is accumulated damage, it is largely preventable with daily sun protection and partly reversible with treatment.
The five markers used to estimate age from a hand are skin texture (surface smoothness and lines), pigmentation or evenness of tone (sun spots), vascularity (vein and tendon prominence), collagen or firmness (elasticity and plumpness), and nail condition. Together they form the basis of a biological hand age estimate.
The hand-to-face age gap is the difference between a person's estimated hand age and face age. Because most people maintain their face with sunscreen and skincare but neglect their hands, hands commonly read 5 to 15 years older. A large gap usually signals treatable, neglected sun damage rather than genetics.
Scan the back of your hand for an age estimate across all five markers, free, in about 15 seconds.
Scan my hands →Related reading:
→ Age estimation from hand appearance: the 5 markers dermatologists check→ Hand age vs face age: what the gap reveals→ How to make your hands look younger: the 90-day routine