Guest blog by Vicky Ware
It’s strange that we take for granted the fact that skin can absorb stuff – for example nicotine from those stickers people use when trying to give up smoking - yet we don’t really think about all the other products we slather on our skin, or allow our skin to come into contact with. Moisturiser, make up, nail varnish, shampoo, clothes washing powder, soap; the list is almost endless.
Nothing in those products is as bad for health as, for example, smoking but the fact is we use a lot of products more than once a day for years. It is this low level long term exposure which has some scientists worried that ingredients in cosmetics might be damaging our health 1.
The skin’s primary role is to act as a barrier; it is there to allow the inside of your body to maintain a different environment to the outside world and to stop microorganisms from passing into your system 2. So, how does your skin absorb some molecules (really small things)?
If a molecule is small enough and has the right chemical properties, it can pass straight through the layers of the skin called the epidermis. Molecules can also pass through glands, or hair follicles. Once through the skin layer they can enter the blood or lymph systems, passing to other areas of the body 3.
The type of skin affects how readily molecules are absorbed, mucous membranes like those inside your mouth absorb much more easily and so does broken skin 3.
Products designed to come into contact with the skin are not really tested in terms of their long term effects on health – because we don’t really think of putting things on our skin in the same way we think of eating, but some of the ingredients are still getting into the blood stream.
One of the chemicals in products which scientists are worried about are phthalates. The term phthalates covers a class of chemicals which are used as ‘plasticisers’ – they are put into plastic to increase certain properties such as flexibility or transparency. They are also in products such as moisturiser because they work as skin moisturisers, softeners and enhance the ability of a product to be absorbed into the skin 1.
Both phthalates themselves and their breakdown products are potentially damaging to health 4, 5,6. They are known to have hormone disrupting effects – and are potentially most damaging when people are exposed to them early in life. For example, exposure to phthalates in the womb has been shown to cause problems with reproductive health in male babies 7.
Exposure has also been linked to causing pregnant women to go into labour sooner than they otherwise would, levels of certain hormones in infants, birth defects in babies 8, and neurobehavioural changes in children 7.
In adults phthalates are linked to decreases in sperm quality in men 9, and reduction in testosterone production 9. Phthalate exposure has also been linked to increases in waist circumference and body mass index, with some scientists suggesting that they may have had a significant role in the obesity epidemic 10.
Worryingly, the highest levels of phthalates in humans are found in reproductively aged women (defined as age 20 to 40 years old) – this might be because these people are using the most cosmetic products 11. Women of this age who had the highest levels of phthalates have been shown to have a lower libido 12.
There are different regulations on phthalates in food and food packaging depending on which country you live in, but there is relatively little regulation on cosmetic ingredients. Often phthalates are not listed in the ingredients, but rather contained under the banner of ‘fragrance’ in the ingredient list – which is why companies often highlight when their product is ‘fragrance free’ 13,8.
Your skin’s ability to absorb things can be used for good, too. It can absorb some essential micronutrients such as magnesium sulfates, which some people may find hard to get enough of via their diet. This can be done by bathing in Epsom salts 14.
Bathing for 12 minutes in water heated to 50-55 degrees centigrade with 3 cups of Epsom salts dissolved in it, once a day for a week resulted in increased levels of magnesium in the blood, suggesting that the people in the study had absorbed the micronutrient from the bath water 14.
Magnesium can be difficult to get via the diet alone because of the difficulty absorbing the mineral from food, eating too few foods which contain it, and because foods which should contain it don’t due to poor soil quality where the food was grown 15. The World Health Organisation has estimated that around 75% of American’s have a deficiency in this essential nutrient, with similar estimates for other first-world countries 16.
Magnesium is essential for your body to function correctly; deficiencies are associated with high blood pressure, heart disease and diabetes – along with a host of other health issues. One reason for this is thought to be that low magnesium levels increase markers of inflammation in the body 17.
Magnesium deficiency is more likely if you have a stressful life, and can then perpetuate problems linked with stress. Therefore, it’s important to ensure you have enough magnesium if you have a stressful lifestyle 18.
Can the ingredients of your deodorant be absorbed through the skin? Yes, but it doesn’t seem that this is a problem to health. At one point scientists thought that deodorant use may be a factor in causing breast cancer, but this is no longer the consensus 19,20. Some studies have shown that deodorant may be harmful 21, some have shown that people using deodorant are LESS likely to get cancer 22, and others have shown it is neither harmful nor protective 23.
When studying the combination of all studies done on the link between deodorant use and breast cancer scientists found an overall protective effect of using deodorant – although they don’t know why this was. While it doesn’t necessarily mean that using deodorant will protect you from cancer it does mean there is unlikely to be a risk from using it 20.
The majority of breast cancers are found in the upper, outer quadrant of the breast (meaning the bit nearest your armpit). This lead some scientists to think that breast cancer might be caused by the application of deodorant 24. However, scientists now think that breast cancer is most likely to appear in this area because this is the densest area of cells in the breast. More cells mean a higher chance of a cancerous cell developing 24.
Aluminium in deodorant was a concern for scientists, and more so for the general public. This began when a study in 2007 found that women who had breast cancer had aluminium in their skin 25 – however, the study didn’t compare women with breast cancer to those without and therefore didn’t really show anything about the correlation of breast cancer to aluminium.
Women are advised to wear aluminium-free (or no) deodorant when they go for breast cancer screening, however this isn’t because there is a link between aluminium containing deodorants and breast cancer, but because the aluminium can show up on the screen making it difficult for Doctor’s to analyse the result. Sort of like wearing metal in a metal detector would stop a Doctor from being able to properly view your bones, wearing aluminium can prevent Doctor’s from seeing the ‘picture’ they take of your breasts properly 26 .
Parabens are another ingredient in deodorant that were thought to be harmful. Evidence from test tube studies (rather than studies in animals or people) found that parabens did increase the risk of cancer developing 19. This might be because parabens are weakly estrogenic – meaning they mimic the effect of oestrogen. However, they are so weakly estrogenic scientists think that they are over-powered by much stronger oestrogenic substances (such as oestrogen itself) when in an actual body, meaning they don’t damage health 27.
It’s thought that the wide-spread idea that deodorant causes breast cancer started with a hoax e-mail 26. The e-mail claimed that antiperspirants caused ‘toxins’ to build up in the body because you were unable to sweat them out. Fortunately, you have your entire surface area of skin to sweat from, not just your armpits, so this is not the case 26.
You can think of your skin as a kind of less-effective intestine, it can absorb things which are put onto it, but not as many things as the intestine can. Despite this, the ingredients in cosmetic products are not as well regulated as those in foods, meaning you could be absorbing ingredients which are bad for health. Unfortunately, labelling is also under-regulated meaning it is difficult to tell which products contain potentially harmful ingredients.
Avoiding cosmetics containing ‘fragrance’ is one way to avoid one of the chemicals known to be harmful such as phthalates. Although it has received a lot of negative press, it doesn’t seem that deodorant has negative health effects. If you’re at all worried there is lots of great information over at the Cancer Research website28. It is also possible to buy aluminium free and paraben free deodorant, even though evidence suggests there is no need for this.
Vicky has a degree in Biological Sciences with a focus on biochemistry and immunology and is currently studying for a MSc in Drug Discovery and Protein Biotechnology. She is also an endurance athlete.
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