Queen Elizabeth I bleached her face with a potentially poisonous lead-based powder to help to hide the ravages of smallpox. Later, the white faces of Venetian courtesans were also achieved with lead-based cosmetics.

But fashions change and now lightly tanned faces are more desirable. Although she was famous for her perfumes, Coco Chanel's penchant for basking on sunny French beaches made deep tans enviable. A tanned complexion was no longer the sign of a peasant, but the hallmark of the leisured classes with the time and money to travel to exotic climes.

Despite the long-term risks of developing skin cancer from severe sunburn, a light tan is still associated with good health, an outdoor lifestyle and sexual allure. Fortunately, as far as the incidence of skin cancer is concerned, a heavy, dark tan is outmoded and more often associated with premature wrinkles and melanomas than vitality and beauty.

For the past 50 years, cosmetics manufacturers, pharmaceutical companies and some university research departments have been trying to discover safer tanning methods. The interest shown by cosmetics manufacturers is not difficult to understand, as a product that either induced accelerated tanning or created a fake tan that looked realistic promised rich returns.

For pharmaceutical companies and universities, the search is on to find a substance that will accelerate the skin's capacity to tan so that fair skinned, blue-eyed blonds and maybe even milky skinned redheads may be exposed to the sun and turn brown safely rather than burn.

Increasingly, cosmetics manufacturers have learnt how to manufacture more natural-looking fake tans. Those that gave users an orange-hued complexion have all but disappeared. However, all these fake tans are only temporary skin dyes that colour its outer layer and don't influence the melanocytes - the cells in the skin that produce the pigment called melanin, which does give a natural tan.

A product called Melasyn, patented by Yale University Medical School, has many of the properties of natural melanin - but although it creates a very natural appearance, it acts only as another temporary dye that will be washed away by hot water and soap once a holidaymaker has returned to the overcast skies of Britain. All skin is constantly being shed and replaced so that false colouration soon fades.

Several cosmetics manufacturers have now added Melasyn to their brands to add verisimilitude to their “tanning” products. Melasyn is closely related to Melanotan, the so-called

Barbie drug, which has the chemical name afamelanotide. But while Melasyn is applied to the skin, Melanotan is given by injection so that it stimulates the melanocytic cells to produce the body's own melanin.

The injectable Melanotan has recently been the subject of an urgent warning by the Government's Medicines and Healthcare Products Regulatory Agency. As Melanotan injections mimic nature's way of producing a tan, why then has it failed to be given a licence in Britain or the US? The disadvantages are that Melanotan hasn't been thoroughly tested and, although doctors know how it darkens the skin, there have been no long-term studies to assess any hidden tendency to induce malignancy, or cause undesirable changes to pigmentation in the long term.

Natural sunlight also stimulates the hormone that causes the melanocyte cells in the skin to secrete more of the pigment melanin that browns the skin. Worryingly, it is the overstimulation of these melanocytes in the epidermal layer of the skin that causes melanomas, the dangerous form of skin cancer.

Its effect on very pale-skinned people, such as redheads or blondes, is also uncertain. Those who are prone to freckling may find that Melanotan increases the number of freckles and also makes them darker. Another side-effect has been noticed in dogs; when injected with Melanotan, the dogs grew jet-black fur.

An increase in pigmentation is attractive only if it is uniform and appropriate. Patchy pigmentation has a tendency to become marked in some people so that unsightly brown stains develop around the eyes and the cheeks, usually wherever there is a hollow or ridge on the face. This is especially noticeable in older people, in women on oestrogen-containing pills and in men having hormone treatment.

Dermatologists are becoming adept at developing laser-based and other therapies to remove these pigmented patches. But once the patient has been in the sun they are likely to reappear. Those wanting less complex treatment, perhaps because they are less seriously affected, may find that Olay's Total Effects skin creams and moisturisers provide some protection against these ageing skin changes, and may lighten discoloured patches.