For dermatologists, there's no question that lightening creams are worrying - 16 think they're only safe when prescribed by a dermatologist, according to a British Skin Foundation survey.
Lesley Saville, skin expert at the International Dermal Institute, agrees that Leona's apparent skin change is down to photographic trickery. "It probably comes down to the lighting or the way they have retouched her rather than her actual skin colour changing. But we have noticed that there seems to be more interest in skin brightening, with a lot of celebrities having more luminous skin.
'The emphasis is on taking better care of your skin, exfoliating and using brightening products which make it look better, but not changing beyond the natural skin colour.
'The problem is when people try to brighten beyond their natural skin colour, that's not a good thing. You're bleaching the skin which is completely contrary to what your skin is designed to do, as your melanocyte cells are designed to make a particular amount of pigment.'"
What products do you need to watch out for?
There aren't many ingredients which will lighten the skin, Lesley explains. Many of the over-the-counter products around will simply even out the skin tone, getting rid of patches of pigmentation, rather than change the overall colour.
The most common whitener is hydroquinone. Unless it's prescribed by a dermatologist or medical professional, hydroquinone is banned in the UK as it can cause long-term damage to the skin. But ,as it is available in the US, it's not difficult to buy online.
"Hydroquinone is a very strong ingredient and can cause hypopigmentation, which is a complete lack of colour in the skin,' says Lesley. 'It can also make skin more sensitive and thinner, as well as causing inflammation which triggers other effects - including more pigmentation. It doesn't give you that even colour. The risks easily outweigh the benefits."
Other common whiteners include Kojic acid and bearberry, both of which have been linked to increased sensitivity, especially if they're used long-term, she explains. Ingredients like liquorice and Vitamin C are brightening, and often found in over-the-counter brightening products, but these also have an effect in stopping the pigment being made so they can turn up in whitening products as well.
If dermatologists prescribe it, surely it's safe?
It's not as simple as thinking a product is fine to use, just because it's legal, explains Lesley. There are potential side effects which the experts will be able to control, but anyone who's using a product on their own won't necessarily know the risks.
When they're looking at treatment, dermatologists use the Fitzpatrick Classification, a grading system of six skin types based on the amount of pigmentation and how likely it is to get more pigmented. Having more pigment in your skin naturally means you're more at risk of conditions like hyper-pigmentation.
"So for example, an Asian person with a burn on their skin is more likely to get a dark pigment mark than a very fair person. If you don't know this you don't know how your skin will respond to a product," says Lesley.
"With products like hydroquinone, dermatologists will make sure the concentration is controlled and you're being closely watched.
'They will also sometimes use high levels of Vitamin A, often known as Retin-A, which causes a lot of cell turnover and helps pigmentation. Because it causes so much exfoliation, you really need to protect your skin with sunscreen, including physical sunscreen blockers, ingredients like zinc oxide and titanium dioxide, otherwise you could end up with even more pigment as the skin becomes very sensitive."
It's also important not to do any further exfoliation or used brightening masks, as this could also overload the skin.
"You're best sticking with what you've got and be happy with that - you are who you are and your skin colour is what it is,' she adds. 'You don't want to mess with nature." Our sentiments exactly!
What are you feelings on skin whitening? Now that you know the facts behind the treatment, leave a comment below and let us know what you think.