As with all our body organs, skin ages as programmed by genes.
This is called internal ageing.
Skin also ages by external factors. Sun is the main external factor that ages the skin.
The sunrays consist of many light spectrums. Ultra violet rays damage the skin most. Both UVA and UVB are responsible for skin damage. Ageing due to sun is called photo ageing.
Sun breaks down the collagen and elastin in the skin.
The skin loses its elasticity and firmness and develops premature wrinkles.
Dark colored individuals show less sun damage while fair skinned people show more sun damage for the same exposure.
With rising age, the total sun exposure increases and its gives rise to not only age spots, but also more serious problems such as actinic keratoses and skin cancers.
The only way to prevent sun damage is protection from the sun.
Gravity plays its part in skin ageing.
As you know gravity pulls everything towards the earth.
As we age, the effect of gravity becomes evident.
The loss of elastin in the skin with ageing plays a role in this. With gravity, jowls form, the ears elongate, the tip of the nose elongates and other such changes take place.