When it comes to sunscreens, it is more difficult to tell which substances are harmful than in a regular moisturizer. First of all, applying thick layers of sunscreen several times a day exposes the skin for much higher doses of the ingredients than a moisturizer. In addition, sunbathing exposes the sunscreen to UV-light, which can cause some of the chemical substances to break down into other more harmful substances, not listed among the ingredients. When we investigated the market to find out what the sunscreens really contain we found that many of the most common sunscreen brands like L'Oréal, Garnier, Neutrogena, Hawaiian Tropic och Lypsyl contained substances that you definitely should avoid in sunscreens, and what is worse, we also found them in sunscreen sprays and lip balms where the risk of inhaling or consuming them is much greater. Unfortunately, not protecting yourself from the sun is a bad option, unless you want to stay in the shadow most of the day. For this reason, we decided to list the most harmful substances that you definitely should avoid when choosing sunscreen.
Ethylhexyl methoxycinnamate / Octinoxate
Ethylhexyl methoxycinnamate (Octinoxate / Octyl methoxycinnamate) is a chemical UVB-filter allowed in the EU at concentrations up to 10% . In 2001, the European Scientific Committee on Consumer Safety concluded that ethylhexyl methoxycinnamate does not have any endocrine disrupting effects. That based on a study that, from what we can conclude, still to this date is unpublished [2,3]. Since then, numerous other studies have shown that ethylhexyl methoxycinnamate has both endocrine disrupting as well as genotoxic properties. It is easily taken up through the skin and can be found in both blood, urine and breast milk [4,5]. A Swiss study from 2008 measured the presence of UV-filters in breast milk and found ethylhexyl methoxycinnamate in the milk from two thirds of all the women participating in the study . A risk assessment of the effects of ethylhexyl methoxycinnamate on various organs came to the conclusion that the limit for maximal concentration allowed today within EU most likely is too high and should be decreased .
If this was not enough, ethylhexyl methoxycinnamate is sensitive to sunlight. It breaks down and changes (isomerizes) when exposed to UV radiation [7,8]. Besides the fact that this diminishes the efficacy of the sunscreen, the breakdown of ethylhexyl methoxycinnamate causes the formation of new products whereof at least one is shown to be genotoxic, that is, can harm the cells' DNA . And protecting the DNA is the foremost reason to use sunscreen.
Regarding the hormone-disrupting effect of ethylhexyl methoxycinnamate, a number of studies have found that it perturbs both the estrogen, progesterone, testosterone and thyroid hormone systems . Most studies are done on rats and not humans and there are clearly contradictory results but nonetheless, it is becoming increasingly clear that ethylhexyl methoxycinnamate exerts a multihormonal effect. The mechanisms behind this are yet unclear och the final effect of such a multihormonal disruption is not necessarily the same between rats and humans and depend a lot on at which age you are exposed to the substance. But even though many things are still unclear, enough is clear to say that ethylhexyl methoxycinnamate is a UV-filter that you should completely avoid in your sunscreen products.
Benzophenone-3 / Oxybenzone
Benzophenone-3 / Oxybenzone is another chemical UV-filter that ever since the 1980's been one of the most common UV-filters in sunscreen. Mostly because it, at least partially, also protects against UVA . Benzophenone-3 is a known photo allergen, that can cause allergies in combination with UV-light [11-13]. Benzophenone-3 is taken up by the skin and can be found in both blood and breast milk . There is a clear connection between the levels of benzophenone-3 in urine and the use of sunscreen . New studies point to a connection between benzophenone-3 and decreased levels of thyroid hormones [15,16], which is especially serious during pregnancy. In addition, in laboratory tests, benzophenone-3 has been shown to bind to several reproductive hormone receptors [17,18]. However, the strength of the binding to the estrogen and progesterone receptors are relatively weak in comparison to the binding estrogen and progesterone hormones. So weak in fact that regarding estrogen and progesterone there are in reality not likely any endocrine perturbing effects, which has also been shown in studies on rats. . However, a study from 2016 indicates an alarming connection between the levels of benzophenone-3 in blood and decreased levels of testosterone in teenage boys . All the effects of benzophenone-3 are definitely not yet clarified and it is also unclear how severely benzophenone-3 perturbs the various endocrine systems.
Last year, EU decreased the maximally allowed limit of benzophenone-3 from 10% to 6% and in addition, the labeling of the product should include the warning ”Contains Benzophenone-3” . A big step forward, but preferably should benzophenone-3 be avoided altogether, especially since there are more and more studies indicating that benzophenone-3 also has a negative impact on marine organisms, being genotoxic for corals  and diminishing reproduction in fish , which is highly disturbing since scientists estimate that several thousand tons of sunscreen reach the coral reefs every year. .
Octocrylene is a chemical UVB and UVA-filter that can cause allergies, especially in combination with sunlight . Avoid if you are overly sensitive to sunscreen products.
Benzylidene camphor sulfonic acid
Benzylidene camphor sulfonic acid another common chemical UV-filter in sunscreen products. A recent study from Denmark has shown that the two UV-filters 3-Benzylidene camphor and Benzylidene camphor sulfonic acid decreased the sperm function and thereby resulted in decreased male fertility . 3-Benzylidene camphor was banned last year within EU because of its endocrine disruptive effects  but benzylidene camphor sulfonic acid is still allowed in concentrations up to 6% .
Formaldehyde releasers are common preservatives in skin care products but can also be found in some sunscreen and after-sun products. Formaldehyde in small amounts decreases the cells' ability to repair the DNA damage caused by the sun's UV-light [26-28]. Both UVA and UVB cause damage to the skin cells' DNA. Most of the DNA-damage is immediately repaired but, if that is not the case, the cell can transform (mutate) into a cancerous cell. When it comes to products that are supposed to protect against the sun and sun damage, is really bad to include substances that impair the reparation of damaged DNA. This increase the risk to develop skin cancer. In our investigation of the content in various sunscreen products, we found formaldehyde releasers in products from among others Eucerin, Neutrogena, Olay, Hawaiian Tropic, L'Oréal, Banana boat och Coppertone. Formaldehyde releasers should always be avoided but be extra cautious when it comes to sunscreen, after-sun and other products you use when you spend a lot of time in the sun. Read more about formaldehyde och formaldehyde releasers in Hidden Formaldehyde in Skin-Care Products – Increased Risk for Skin Cancer?
Tween, Polysorbate and Polyoxyethylene
When ethoxylated surfactants like the emulsifiers tween-80, polysorbate and polyoxyethylene are exposed to heat or light, they oxidize, breaks down and form, among other things, formaldehyde [29-31], which diminishes the cells' ability to repair the DNA damage caused by the suns' UV-light [26-28]. See formaldehyde releasers above.
Methylisothiazolinone is a highly allergenic preservative . As of February this year, methylisothiazolinone is prohibited in leave-on products within the EU and thereby also in sunscreen products. However, in many other parts of the world, like the US, there are no restrictions to use methylisothiazolinone in sunscreen products, so check the ingredients list if you plan to buy your sunscreen abroad.
Sunscreen in spray form has become increasingly popular and might seem practical. However, with sprays, there is a great risk to inhale dangerous substances and, at the same time, they result in an uneven sun protection. Mainly this risk concerns endocrine disrupting substances and nanoparticles of zinc oxide and titanium dioxide, but to be on the safe side, it is best to avoid spray-on sunscreen altogether.
- CosIng, European Commission Cosmetic ingredient database, Annex VI , List of UV filters allowed in cosmetic products.
- SCCNFP Opinion on the Evaluation of Potentially Estrogenic Effects of UV-filters adopted by the SCCNFP during the 17th Plenary meeting of 12 June 2001. 2001 Available at: http://ec.europa.eu/health/scientific_committees/consumer_safety/opinions/sccnfp_opinions_97_04/sccp_out145_en.htm [Accessed; May 2018]
- Bolt, H.M. et al., Comments on "In vitro and in vivo estrogenicity of UV screens". Environ Health Perspect, 2001. 109(8): A358-61.
- Schlumpf, M. et al., Endocrine Active UV Filters: Developmental Toxicity and Exposure Through Breast Milk. CHIMIA International Journal for Chemistry, 2008. 62(5): 345-351.
- Janjua, N.R. et al., Systemic absorption of the sunscreens benzophenone-3, octyl-methoxycinnamate, and 3-(4-methyl-benzylidene) camphor after whole-body topical application and reproductive hormone levels in humans. J Invest Dermatol, 2004. 123(1): 57-61.
- Klammer, H. et al., Multi-organic risk assessment of estrogenic properties of octyl-methoxycinnamate in vivo A 5-day sub-acute pharmacodynamic study with ovariectomized rats. Toxicology, 2005. 215(1-2): 90-6.
- Jentzsch, F. et al., Photodegradation of the UV filter ethylhexyl methoxycinnamate under ultraviolet light: Identification and in silico assessment of photo-transformation products in the context of grey water reuse. Sci Total Environ, 2016. 572: 1092-1100.
- Pattanaargson, S. et al., Photoisomerization of octyl methoxycinnamate. Photochemistry and Photobiology, 2004. 161(2-3): 269-274.
- Sharma, A. et al., Different DNA damage response of cis and trans isomers of commonly used UV filter after the exposure on adult human liver stem cells and human lymphoblastoid cells. Sci Total Environ, 2017. 593-594: 18-26.
- Lorigo, M. et al., Photoprotection of ultraviolet-B filters: Updated review of endocrine disrupting properties. Steroids, 2018. 131: 46-58.
- Scientific Committee on Consumer Products (SCCS), Opinion on Benzophenone-3, 2008.
- Berne, B. and Ros, A.M., 7 years experience of photopatch testing with sunscreen allergens in Sweden. Contact Dermatitis, 1998. 38(2): 61-4.
- Rodriguez, E. et al., Causal agents of photoallergic contact dermatitis diagnosed in the national institute of dermatology of Colombia. Photodermatol Photoimmunol Photomed, 2006. 22(4): 189-92.
- Berger, K.P. et al., Personal care product use as a predictor of urinary concentrations of certain phthalates, parabens, and phenols in the HERMOSA study. J Expo Sci Environ Epidemiol, 2018.
- Kim, S. et al., Considering common sources of exposure in association studies - Urinary benzophenone-3 and DEHP metabolites are associated with altered thyroid hormone balance in the NHANES 2007-2008. Environ Int, 2017. 107: 25-32.
- Aker, A.M. et al., Associations between maternal phenol and paraben urinary biomarkers and maternal hormones during pregnancy: A repeated measures study. Environ Int, 2018. 113: 341-349.
- Balazs, A. et al., Hormonal activity, cytotoxicity and developmental toxicity of UV filters. Ecotoxicol Environ Saf, 2016. 131: 45-53.
- Schlumpf, M. et al., In vitro and in vivo estrogenicity of UV screens. Environ Health Perspect, 2001. 109(3): 239-44.
- Scinicariello, F. and Buser, M.C., Serum Testosterone Concentrations and Urinary Bisphenol A, Benzophenone-3, Triclosan, and Paraben Levels in Male and Female Children and Adolescents: NHANES 2011-2012. Environ Health Perspect, 2016. 124(12): 1898-1904.
- Commission Regulation (EU), 2017. /238.
- Downs, C.A. et al., Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands. Arch Environ Contam Toxicol, 2016. 70(2): 265-88.
- Rodriguez-Fuentes, G. et al., Evaluation of the estrogenic and oxidative stress effects of the UV filter 3-benzophenone in zebrafish (Danio rerio) eleuthero-embryos. Ecotoxicol Environ Saf, 2015. 115: 14-8.
- de Groot, A.C. and Roberts, D.W., Contact and photocontact allergy to octocrylene: a review. Contact Dermatitis, 2014. 70(4): 193-204.
- Rehfeld, A. et al., Chemical UV Filters Mimic the Effect of Progesterone on Ca2+ Signaling in Human Sperm Cells. Endocrinology, 2016. 157(11): 4297-4308.
- Scientific Committee on Consumer Safety (SCCS), Opinion on 3-Benzylidene camphor, 2013.
- Luch, A. et al., Low-dose formaldehyde delays DNA damage recognition and DNA excision repair in human cells. PLoS One, 2014. 9(4): e94149.
- Emri, G. et al., Low concentrations of formaldehyde induce DNA damage and delay DNA repair after UV irradiation in human skin cells. Exp Dermatol, 2004. 13(5): 305-15.
- Grafstrom, R.C. et al., Formaldehyde damage to DNA and inhibition of DNA repair in human bronchial cells. Science, 1983. 220(4593): 216-8.
- Bergh, M. et al., Contact allergenic activity of Tween 80 before and after air exposure. Contact Dermatitis, 1997. 37(1): 9-18.
- Bergh, M. et al., Formation of formaldehyde and peroxides by air oxidation of high purity polyoxyethylene surfactants. Contact Dermatitis, 1998. 39(1): 14-20.
- Dahlquist, I. et al., Detection of formaldehyde in corticoid creams. Contact Dermatitis, 1980. 6(7): 494.
- Scientific Committee on Consumer Safety (SCCS), Opinion on Methylisothiazolinone, 2015.