At first it doesn't really bother us. We may find our skin's a little less firm or toned and our jowls a bit floppy... This is because from around the age of 25, our skin loses 1% of its collagen every year - a slow process that's made worse by exposure to the sun, smoking and lack of sleep. As the years pass, our facial contours lose their chiselled look. These early signs of ageing skin often creep up on our cheeks and cheekbones, when we'll notice that our faces have begun to sag. The reason? Our bodies start to produce less collagen and elastin fibres - the two proteins that govern skin density and provide our faces with an inner scaffold. To put it simply, this means our skin is no longer held up and the effects of gravity begin to take hold. As our skin slackens, wrinkles and lines appear - the infamous 'expression lines' that add character to our faces. And the second skin-ageing factor? A decrease in hyaluronic acid that's naturally present in our skin.