Melanoma skin cancer

Could the cosmetic products we use be harming our health in any way? A while back, Henry neatly debunked the persistent myth that deodorants are linked to breast cancer. Today, another study comes out that turns the spotlight on another group of products – moisturising creams.

The study found that common moisturising creams can increase the risk of skin cancer in mice that had already experienced high doses of ultraviolet (UV) radiation, mimicking the effect of heavy sun exposure. Let’s take a closer look at the results.

What they found

The study, published in the Journal of Investigative Dermatology, comes from a team of American researchers led by Yao-Ping Lu, who practically stumbled across their results by accident. They were actually following up on an earlier study, where they found that applying caffeine to the skin of mice could reduce their chances of developing skin cancer, after being exposed to UV radiation.

Obviously, smearing coffee beans over your face isn’t ideal, so the team wanted to develop a ‘caffeine cream’ based on every-day skin moisturisers. But first, they thought it’d be best to be sure that the moisturisers themselves were completely safe. And to their surprise, they weren’t.

First, they shone heavy doses of UV radiation (of the type that leads to sunburn and skin cancer) on the mice twice a week for 20 weeks. After that, some of the mice were left alone, and others were treated with Dermabase moisturiser once a day, 5 times a week for 17 weeks.

They found that the moisturised mice were twice as likely to develop non-melanoma skin cancers (NSMCs) as their untreated peers, and to develop them in greater numbers. Half of the treated mice developed NMSCs, compared to one in four of the untreated ones. Other types of moisturiser, including Dermovan, Eucerin and Vanicream also had the same effect.

The team also tried treating the UV-exposed mice with water alone to see if their increased risk of cancer was just an effect of placing anything on their skin. It wasn’t – the water didn’t do anything.

A word of caution

So does this mean that moisturisers cause cancer? Not quite – but it does highlight some questions that need to be addressed with more research.

For a start, non-melanoma skin cancer is more common in men, even though women are more likely to use moisturisers. The rates of NMSC in the UK population have effectively provided us with a ‘natural experiment’, which shows that even if moisturisers can boost the effects of UV damage, they don’t play a major role in this type of skin cancer.

It’s also important to note that the study was done in mice and, for the moment, we have no idea if the same thing would happen to humans. Mouse skin is very different to human skin, and we’re not just talking about the fur; mouse hide is thinner than ours and absorbs chemicals more readily. So making any assumptions about the effects of moisturisers on human skin is extremely premature.

Also, these mice already had a naturally high risk of skin cancer, and they were bombarded with so much UV radiation that even a quarter of the unmoisturised mice developed NMSC. In fact, six in seven of them developed some sort of skin tumour.

So it’s unlikely that the moisturisers directly cause cancer. It’s much more likely that they’re just aggravating the effects of UV radiation, which we know can cause skin cancer by damaging the DNA of skin cells.

In fact, the authors of the paper speculate that these products could have worsened the effects of existing DNA damage by causing inflammation, and encouraging the damaged cells to start dividing.

Playing it safe

So if (and it’s a big if) moisturisers and UV radiation interact in the same way on human skin, there is a way of preventing this from happening – avoid heavy exposures to UV radiation. Indeed, our SunSmart campaign already advises people to do this, while enjoying the sun sensibly..

In the meantime, the study raises a few questions that are worth answering:

  • This is the first study to look at the combined effects of moisturiser use and heavy UV exposure. The results are interesting, and need to be repeated in other experiments.
  • We need to see if the results apply to human skin.
  • NMSC is very common but the vast majority are effectively removed through surgery. We need to see if these products could affect the development of melanoma, a rarer but more dangerous type of skin cancer.
  • The researchers looked at the ingredient lists of the moisturisers and identified two ingredients that they thought may have been responsible for the problems: sodium lauryl sulphate and mineral oil. Without these ingredients, the moisturisers no longer had any effect on the mice. These ingredients are commonly used in cosmetic products, so it’s important to understand exactly how these chemicals interacted with heavy UV radiation exposure to affect the risk of skin cancer.

It’s far too early to come to any conclusions about these chemicals, or to worry if you use products that contain them.

If you are concerned about NMSC, the best thing to do is to stay safe in the sun, and avoid the type of heavy exposures that lead to reddening or burning. If you follow this advice, there is no reason to believe that these products would do you any harm.