The skin under the eye is the thinnest on the face and therefore the most prone to 'mechanical' lines – those created by repeated actions, such as frowning. Tugging or rubbing the skin can also create lines so you need to apply make-up with care. When using concealer on under-eye circles, liquid formulations cause the least friction – but don't always offer the best coverage. Instead, go for creamier solid formulations. Warm the concealer up first, either by running your finger over the surface so it begins to soften or by adding a little to the back of your hand and taking it from there. Then apply with either a brush – not too small as this will put more pressure on the skin – or the third finger of the left hand, which tends to be the weakest and therefore applies least pressure. Whatever you do, don't use hard pencil concealers directly on the under-eye area as they'll drag the skin and can break small blood vessels beneath, thus only adding to shadows.