Parabens … the word itself evokes controversy, and for multiple reasons. Parabens have been implicated in the development of cancer (new data suggest that contrary to previous studies, clinically relevant concentrations of parabens can too, stimulate the growth of cancer when combined with natural growth hormones in breast tissues (1)), skin allergies (a small but real occurrence, ranging from 0-4.2% in populations (2)), and skin aging. The focus of this article will deal with skin aging and involves methylparaben in particular.
Whether you are an anti-aging aficionado who values sunscreens, anti-aging serums, and masks; a make-up enthusiast; use skincare for problematic skin (dry skin, acne, etc.), or simply prefer to keep it basic with just a cleanser and sunscreen, it is highly likely that you have been unknowingly unexposed to methylparaben through one or multiple skincare products (I know I have!).
- What methylparaben is
Skincare products, regardless of whether they are serums, creams, lotions, or thick masks, need preservatives to prevent the growth of bacteria, mold, and fungi that is bound to occur in all formulations. Parabens are ubiquitous in skincare because they are highly effective against these disease-causing microbes and are inexpensive. The most common paraben found among cosmetics is methylparaben, a methyl ester of p-hydroxybenzoic acid. At a molecular weight of 152 g/mol, it can easily travel across all the layers of the skin, from the stratum corneum to the dermis. It is used in concentrations anywhere from 0.1-0.4% (15), but these levels are not as insignificant as they appear.
So, what are the cosmetic consequences of methylparaben?
- It significantly increases UV damage to skin (sunscreen is NOT a cure)
In an in vitro study, tiny concentrations of methylparaben (.003%) and low-dose UVB light —- which both did not elicit strong negative effects on human skin cells when administered separately -— reacted synergistically and produced dramatic deleterious effects on skin cells. Such effects included increases in oxidative stress, lipid peroxidation, and inflammatory markers, all of which contribute to UVB-induced damage of skin. (8)
In another in vitro study, it was found that a particular photoproduct derived from the interaction of methylparaben and UV light — 3-hydroxy methyl paraben — spawned an active metabolite in dermal tissue that led to oxidative DNA damage. (9) In addition to accelerated aging of the skin, on a more serious note, this can lead to carcinogenesis. This might partly explain the occasional findings of sunscreen use being associated with a greater risk for malignant melanoma (apart from the obvious explanations: more overall sun exposure, low SPF formulas used, and inadequate amounts used).
The extrapolation to human skin in real-life conditions from these findings has been criticized since the aforementioned studies were done in vitro and were analyzed in aqueous solutions, which probably elevated the amount of UV damage. Still, the substantial increase in oxidative stress, inflammation, and cell death is not a good sign and even if the degree of damage is inhibited somewhat on dry human skin, the amount of increased damage is likely to still be significant. Moreover, it was recently found that a sizable increase in phototoxicity was corroborated in an in vivo study with hairless mice. In this study, practical concentrations of methylparaben and related substances (e.g., propylparaben) in a gel-cream formulation topically applied to the bare backs of the animals considerably increased the amount of damage in UV-exposed skin when compared to the same amount of irradiation without the paraben-containing formulation. The UV dosage here was not by any means excessive; in fact, it merely simulated natural UV conditions on a summer day.
Interestingly, this study also analyzed the effects on skin when a sunscreen was included in the paraben formulation. In this short-term study, the changes of the skin did not differ significantly from the control group (no irradiation and no paraben exposure), although the authors noted that the phototoxic ingredients (parabens) in the sunscreen’s formulation was likely still producing oxidative stress — albeit to a lesser extent — which probably demanded antioxidant defenses from the skin cells, which cannot be substituted for long-term protection, as they are finite. (10) Since the UV exposure was extremely short-term (irradiation occurred for 15 minutes once a day for 5 consecutive days (11) ), it was not sufficient to recognize just how much extra damage was occurring in the skin that was exposed to parabens and simultaneously protected with sunscreen. Moreover, the study did not include a paraben-free sunscreen group, so the increase in skin damage that would have likely occurred in the sunscreen+parabens group in comparison to the paraben-free sunscreen group could not be assessed.
What is definitely known is that no sunscreen protects the skin completely from the sun and that parabens potentiate UV damage in vivo. With this information at hand, it is reasonable to assume that by using a paraben-containing sunscreen versus a paraben-free sunscreen, more negative skin changes will accrue over time than if a sunscreen without parabens was used. How noticeable this extra damage would be is currently unknown, however. Although methylparaben is the paraben being discussed, it is worth noting that propylparaben displayed the most phototoxic response in the aforementioned study (10), and this substance is often used together with methylparaben in many skincare products.
- It decreases collagen formation, regardless of UV exposure
Even if wearing sunscreen could entirely alleviate the enhancement of UV-induced skin damage, there is a whole other problem that occurs independently of UV exposure that will not be accounted for, and that is methylparaben-mediated decreases in collagen. When sun exposure is totally factored out of the equation, long-term exposure of minuscule amounts of methylparaben to normal neonatal human epidermal keratinocytes decreased the expression of type IV collagen. Methylparaben furthermore decreased enzyme activity responsible for the production of hyaluronic acid (5) —another essential skin component that promotes cell proliferation and protects against skin atrophy, while also preserving moisture, plumpness, and indirectly, improving elasticity and the appearance of wrinkles (12)). In this very study, it was also found that methylparaben affected the proliferation rate and cell morphology, indicating that long-term exposure may additionally lead to an abnormally disorganized epidermis. (5)
These results were supported and expanded upon in a very recent study with human dermal fibroblasts (dermal skin cells). Here, methylparaben was found, in small concentrations, to dose-dependently decrease collagen biosynthesis. Multiple collagen types (type I, III, IV) was shown to be decreased in their expression at the mRNA level. Besides inhibiting collagen synthesis, methylparaben also stimulated collagen-digesting enzymes, which further contributed to the markedly decreased collagen content observed in the medium. Methylparaben predictably interfered with cell proliferation, cell viability, and also inhibited cell survival (13). The negative effect on cell viability was not observed in the previous study, but that is probably because concentrations in this study were 10-fold higher, yet still normal in terms of the amounts found in cosmetics.
The adverse influences of methylparaben on collagen, hyaluronic acid, and viability of the skin cells themselves have not yet been studied in vivo, but these preliminary results should be highly disconcerting to anyone interested in skin health.
- Accumulation … adding insult to injury
Methylparaben exerts the significant aforementioned effects with relatively low concentrations, and these ravaging effects worsen with increasing concentrations. Methylparaben concentrations were thought to be swiftly metabolized by skin enzymes called esterases, but it turns out that these enzymes break down methylparaben at a slower rate than what was thought, causing the agent to accumulate in skin layers, especially if products containing methylparaben are used more than once within a 36 hour period (4)***, which is very typical for cosmetic products such as sunscreens, moisturizers, lip color, and powders.
(***Interestingly, other authors have used this same study to claim that methylparaben does not have cumulative effects after 36 hours, but this is only based on one of the experiments, which had to do with just a single dose of paraben exposure. In the other experiment in which methylparaben exposure was repeated after every 12 hours — which, again, is a realistic frequency of exposure given how often a product is used and/or given that a number of products containing methylparaben can easily be used throughout a day — significant cumulative effects most certainly did occur, and showed practically linear accumulation after 12 hours, which was considerably increased by 36 hours.)
When a small cosmetically-relevant concentration (0.15% of the formulation) of methylparaben was applied on the forearm twice a day, the amount of methylparaben in the stratum corneum (SC) doubled by one week from the amount detected 12 hours after the first application. By one month, the concentration in the SC increased 12-fold from the initial recording! After complete cessation of use, the concentration in the SC decreased dramatically by 48 hours, although levels were still a little higher than the baseline readings. (5) These findings are startling when you consider that methylparaben is absorbed much more efficiently on the face. (13)
Worse, many methylparaben-containing product also consist of other ingredients that can directly and indirectly lead to a greater accumulation in skin, alcohol being a prime example. Alcohol has shown to slow down the ability of esterases to break down methylparaben in vitro, and additionally, it enhanced dermal absorption of the fiendish paraben in guinea skin, also in vitro. (6,7) Alcohol is a known penetration enhancer of topically-applied substances in human skin, so it is not a stretch to assume that by using products containing methylparaben and alcohols, its accumulation in the skin would rise due to the increasing of its penetration and the reduced effectiveness of its breakdown.
- Skincare containing methylparaben
Methylparaben is found within the full variety of skincare products: cleansers, moisturizers, anti-aging serums/lotions/serums, sunscreen products, self-tanners, acne creams, primer, foundation, bronzers, make-up remover, chapstick, lipstick, eyeliner, masks, and also in a preservative product that many who use DIY skincare might be familiar with, Germaben II.
List of brands that contain methylparaben:
(Caveat: These are simply the brands that I’ve come across that contain methylparaben in one or more of their products. There are countless other brands that include the paraben in their formulas, and so it is strongly recommended to check the labels of ALL brands of cosmetics. In the same token, one should not feel the need to exclude an entire brand that is listed below, as most of their other products might not have methylparaben in their formula. It is important to scrutinize each individual product’s label carefully, no matter what the brand may be.)
Clean & Clear
- Alternatives to methylparaben (and parabens in general)
No matter what, the need to include preservatives in cosmetic formulations to protect against microbial growth of germs is essential. Fortunately, there are valid alternatives to look for. Other paraben-free (and formaldehyde-free!) preservatives that are effective and widely-used are phenoxyethanol, sodium benzoate, potassium sorbate, Neolone, OptiphenPlus, Hydantoin, Glycacil, Natrulon and benzethonium chloride. (14)
- Goodman B. FAQ: Parabens and Breast Cancer [Internet]. WebMD. WebMD; 2015 [cited 2018May20]. Available from: https://www.webmd.com/breast-cancer/news/20151027/parabens-breast-cancer#1
- Garner N, Siol A, Eilks I. Parabens as preservatives in personal care products. Chemistry in Action. 2014;103:36-43.
- Methylparaben [Internet]. EWG. [cited 2018May20]. Available from: https://www.ewg.org/
- El Hussein S, Muret P, Berard M, Makki S, Humbert P. Assessment of principal parabens used in cosmetics after their passage through human epidermis–dermis layers (ex‐vivo study). Experimental dermatology. 2007 Oct 1;16(10):830-6.
- Ishiwatari S, Suzuki T, Hitomi T, Yoshino T, Matsukuma S, Tsuji T. Effects of methyl paraben on skin keratinocytes. Journal of applied toxicology. 2007 Jan 1;27(1):1-9.
- Lakeram M, Paine AJ, Lockley DJ, Sanders DJ, Pendlington R, Forbes B. Transesterification of p-hydroxybenzoate esters (parabens) by human intestinal (Caco-2) cells. Xenobiotica. 2006 Jan 1;36(9):739-49.
- Kitagawa S, Li H, Sato S. Skin permeation of parabens in excised guinea pig dorsal skin, its modification by penetration enhancers and their relationship with n-octanol/water partition coefficients. Chemical and pharmaceutical bulletin. 1997 Aug 15;45(8):1354-7.
- Handa O, Kokura S, Adachi S, Takagi T, Naito Y, Tanigawa T, Yoshida N, Yoshikawa T. Methylparaben potentiates UV-induced damage of skin keratinocytes. Toxicology. 2006 Oct 3;227(1-2):62-72.
- Okamoto Y, Hayashi T, Matsunami S, Ueda K, Kojima N. Combined activation of methyl paraben by light irradiation and esterase metabolism toward oxidative DNA damage. Chemical research in toxicology. 2008 Jul 26;21(8):1594-9.
- Hossy BH, da Costa Leitão AA, dos Santos EP, Matsuda M, Rezende LB, Rurr JS, Pinto AV, Ramos-e-Silva M, de Pádula M, de Oliveira Miguel NC. Phototoxic assessment of a sunscreen formulation and its excipients: An in vivo and in vitro study. Journal of Photochemistry and Photobiology B: Biology. 2017 Aug 1;173:545-50.
- Hossy BH, da Costa Leitao AA, Luz FB, Dos Santos EP, Allodi S, de Pádula M, de Oliveira Miguel NC. Effects of a sunscreen formulation on albino hairless mice: a morphological approach. Archives of dermatological research. 2013 Aug 1;305(6):535-44.
- Göllner I, Voss W, von Hehn U, Kammerer S. Ingestion of an Oral Hyaluronan Solution Improves Skin Hydration, Wrinkle Reduction, Elasticity, and Skin Roughness: Results of a Clinical Study. Journal of evidence-based complementary & alternative medicine. 2017 Oct;22(4):816-23.
- Majewska N, Zaręba I, Surażyński A, Galicka A. Methylparaben‐induced decrease in collagen production and viability of cultured human dermal fibroblasts. Journal of Applied Toxicology. 2017 Sep 1;37(9):1117-24.
- Formaldehyde- paraben free preservatives [Internet]. Formaldehyde & Paraben Free Preservatives – Preservativesindia. [cited 2018Jun1]. Available from: http://preservativesindia.com/formaldehyde-paraben-free-preservatives.htm
- Preservative directory. [Internet]. HighBeam Research – Newspaper archives and journal articles. The Washington Post; [cited 2018Jun1]. Available from: https://www.highbeam.com/