Skin does not pay the bill in August. It pays it in September, when the sun weakens, summer packs up and suddenly there is a face in the mirror that looks different from the one in June. By then it is too late to fix, and all five mistakes that led there were free to avoid.

One: everything goes on the face, nothing on the rest. Skincare specialist Carmen Navarro puts it most briefly - caring for skin means doing it globally. Sun cream, after-sun and moisturiser almost always end up on the face, while the neck, décolletage and hands are left out. That is exactly where ageing shows most, because nobody looks there until it becomes obvious.

Two: you sleep badly and assume it does not count. Dr Lara Victoria points out that summer wrecks every routine - late evenings, hot nights, shifted wake-up times. Skin regenerates while we sleep, and if that process is constantly interrupted, the daily damage simply accumulates. Three weeks of holiday on five hours of sleep a night is not a holiday for your skin.

Three: the afternoon sun is supposedly harmless. This is the most expensive misconception of them all. "Skin does not age only from the amount of sun, but also from the hour at which it receives it," says Dr Lara Victoria. Many stop applying cream around four in the afternoon, feeling the risk has passed. Ultraviolet radiation does not work to our schedule.

Four: diet is treated as a separate topic. Carmen Diaz, a skin specialist and director of a cosmetic centre, recommends a varied diet rich in antioxidants to neutralise the oxidative effect of free radicals on cells. Vitamin A from carrots and spinach, vitamin C from citrus, vitamin E from walnuts and vegetable oils. Nothing exotic and nothing you will not find at any market here.

Five: cream goes on once and is forgotten. The rule is to apply it twenty minutes before going out, on dry skin, and to repeat every two hours or immediately after swimming. The forgotten zones are always the same - the tops of the feet, the crown of the head and the back of the neck.

None of these five steps requires new cosmetics, a treatment or money spent. They only require you to stop assuming your skin will cope because it has coped so far. It does cope - and then it shows you the bill in September.