After all, all moisturisers do the same job don't they? Well, yes and no.

The job of a moisturiser is to keep the outer layer of the skin pliable and less likely to crack, making it feel soft and smooth. This is mainly achieved by slowing down moisture loss from the skin (water constantly evaporates from it) by creating a physical barrier. The difference between day and night products is in the formulation or the added extras.

Night cream vs day cream

Night creams tend to contain higher levels of active ingredients such as retinol, vitamin C and alpha hydroxy acids (AHA's) to help boost skin repair as well as moisturising it. Day creams on the other hand focus on hydrating the skin whilst also protecting it from the environment, from UV light and pollution for example, with sunscreens and anti-oxidants. Whilst you wouldn't do your skin any harm by wearing day cream at night and vice versa, you don't need an SPF when the sun goes down. Also some of those active regenerating ingredients can either be broken down by UV and rendered ineffective or can make your skin more sensitive in the sun.

Research has shown that your skin reacts differently according to your body clock too. During the day, the skin's energies are directed at protecting itself and you from stress, be it environmental or psychological. At night however, cells focus on repairing themselves and damage sustained during the day. It follows that using different products for night and day supports the natural functions of the skin.

Do I need a night cream?

But does everyone need a night cream? According to dermatologist Dr Leslie Baumann, Chief of the Division of Cosmetic Dermatology at the University of Miami School of Medicine, the important thing is to first know your skin type. For example, she says, 'oily types do not need a night cream unless for a treatment such as to reduce inflammation or get rid of dark pigmentation patches'.

Dr Leslie has divided people into 16 skin types in her book 'The Skin Type Solution', Hodder Mobius, £16.99 (if you thought there was only dry, normal, combination and oily – think again!). The types are based on a combination of the following:

oily versus dry

sensitive vs resistant (sensitive means acne, redness, flushing, burning)

pigmented vs non-pigmented (unwanted dark spots or not)

wrinkled or not wrinkled (how tight your skin is)

Broadly she says that if you are dry, you need a hydrating night cream. Sensitive skin needs an anti-inflammatory night cream. For pigmented skin go for lightening ingredients in your cream, while for wrinkles go for retinol or antioxidants. You can follow these guidelines by reading cosmetic labels or asking at beauty counters. Her book also helps you pinpoint your exact skin type and usefully tells you which products contain which ingredients (2000 are listed).

So, if you want your skin to look better for longer, do buy separate products for day time protection and night time treatment and repair. Just make sure they're right for your skin type and, most importantly, that you like the smell and texture of your products, so using them is enjoyable rather than a chore.

Read Eve's top recommended night creams for different skin types

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