Is homemade sunscreen a recipe for disaster?

A June 2024 video, posted to the social media website TikTok, depicted the making of homemade sunscreen.1 The video has since amassed more than 20 million views and two million “likes.”1 Numerous recipes posted online claim to create a product with safer “natural” ingredients compared to commercially available sunscreens, for a fraction of the cost. This article discusses these recipes, their claims and the potential risks of using homemade sunscreen.Which ingredients are typically used?The TikTok video referred to earlier involved a concoction of coconut oil, beeswax, shea butter, cocoa butter and jojoba oil. These ingredients were melted and mixed over a pot of boiling water, followed by the incorporation of zinc oxide powder. No specific quantities for any ingredients were stated. The resulting liquid product was poured into a glass jar and placed in the refrigerator where it formed a solid with a wax-like consistency.Recipes primarily use zinc oxide powder as the active ingredient, combined with a carrier oil (e.g., coconut oil, sweet almond oil, avocado oil, olive oil or carrot seed oil), plus beeswax or shea butter as a thickening agent. Some recipes add essential oils, vitamin E oil or aloe vera gel, with cocoa powder as an option to help better match the product to skin tones.2,3Claims made about homemade sunscreenOne website providing a recipe for homemade sunscreen states that “most [commercial] sunscreen does not help avoid skin cancer and may actually increase the chances of it.”2 Claims of this nature are often rationalized by citing:Safety concerns related to the use of nanoparticle-size zinc oxide in commercial sunscreens. The importance of using “non-nano” zinc oxide powder, with particle dimensions larger than 100 nanometres, is emphasized in these recipes to reduce systemic absorption.Studies reporting a positive association between sunscreen use and melanoma development.4-7Benefits related to avoiding the ultraviolet (UV) light-absorbing agent oxybenzone are also commonly mentioned. This is due to concerns about endocrine disruption,8 and negative effects on marine life when it washes off of swimmers,9 prompting bans on it and related ingredients by some popular travel destinations including Hawaii, Aruba and the U.S. Virgin Islands.10Finally, websites often make claims about additional sun protection factor (SPF) benefits offered by adding various essential oils to base recipes. However, these claims are based on a study that calculated SPF values of various oils in vitro (as part of 0.1% stock solutions within an ethanol and water solution), and did not study protection offered by oils mixed within cream bases or upon application to human skin. Reported values from this testing ranged from 7.549 for olive oil and 7.119 for coconut oil to 0.248 for rose oil.11 However, actual protection offered from adding oils to these recipes is uncertain and may not meet the minimum SPF of 30 recommended by the Canadian Dermatology Association.12The evidenceMost research on zinc oxide nanoparticles has found no penetration through the skin.13 One study examining topically applied isotope-traced zinc oxide sunscreen reported that systemic absorption through sun-exposed skin was higher with nanoparticles averaging 19 nm in size versus particles over 100 nm in size; however, the proportion absorbed was low overall at < 0.001% of the applied dose.14 Zinc oxide nanoparticles are more efficient filters of UV light compared to larger particles.12 With the risk of systemic exposure being low, the benefits of using zinc oxide nanoparticles in sunscreens must be noted, as UV exposure is a well-established cause of skin cancer.15After examining the limitations of studies reporting rising melanoma incidence rates over time despite increased sunscreen use, several hypotheses other than exposure to ingredients in sunscreen have been proposed for this association, including:16Increased awareness, detection and reporting of melanomaClimate change resulting in an increased UV index and more time spent outdoors due to warmer temperatures17,18Sunscreen use being associated with a longer duration of sun exposure, especially when sun exposure is intentional,19 which is often the case among travellersInadequate sunscreen application, including insufficient quantity applied, inadequate coverage of exposed areas, and suboptimal frequency of re-application.20The latter two hypotheses form part of the “sunscreen paradox,” which is defined as the phenomenon where “individuals with higher levels of sun exposure also tend to use more but not an adequate quantity of sunscreen or other sun-protection measures, providing a false sense of security.”21 Sunlight avoidance measures, such as seeking shade or other forms of coverage, may also be pursued to a lesser extent when individuals feel protected through sunscreen.Other formulation-related concerns for homemade sunscreen have been published in a statement from the American Academy of Dermatology, including unknown SPF protection, uncertain water resistance, inconsistencies between batches or within a batch due to improper mixing, and unknown shelf-life.22SummaryTravellers and those enjoying a “staycation” close to home who are looking for sunscreen alternatives should be informed of the safety evidence related to zinc oxide nanoparticles and the known risks of UV exposure. Commercially made and tested sunscreens from reputable manufacturers are available that are free of oxybenzone and parabens, and also have rigorous testing and quality control to ensure safety and effectiveness. Pharmacies should stock and encourage patients to use products recognized by the Canadian Dermatology Association, with a complete list available at https://dermatology.ca/public-patients/recognized-products/sunscreen/. Compounding pharmacies may also be able to formulate mineral sunscreens to meet specific patient needs and preferences; however, compounded products cannot claim an SPF designation without having been tested for such.23One in three cancers diagnosed worldwide is a form of skin cancer, of which 80%–90% are attributable to exposure to UV radiation.24 Taking chances with sun protection by using homemade sunscreen is simply not worth the risk.Sherilyn Houle is an associate professor, School of Pharmacy, University of Waterloo, ON, She has her Certificate in Travel Health from the International Society of Travel Medicine (ISTM) and has been recognized with Fellow status in the ISTM for her contributions to the field of travel medicine.References:Freedman A. Homemade sunscreen doesn’t work, despite what TikTok tells you. (accessed November 26, 2024).Wellness Mama. Natural homemade sunscreen recipe. (accessed November 26, 2024).Our Amyable Farmhouse. A natural sunscreen made at home with simple, healthy ingredients that actually work and no white residue. (accessed November 26, 2024).Huncharek M, Kupelnick B. Use of topical sunscreens and the risk of malignant melanoma: a meta-analysis of 9067 patients from 11 case-control studies. Am J Public Health 2002;92:1173-7.Wolf P, Quehenberger F, Müllegger R, et al. Phenotypic markers, sunlight-related factors and sunscreen use in patients with cutaneous melanoma: an Austrian case-control study. Melanoma Res 1998;8:370-8.Gorham ED, Mohr SB, Garland CF, et al. Do sunscreens increase risk of melanoma in populations residing at higher latitudes? Ann Epidemiol 2007;17:956-63.Radespiel-Troger M, Meyer M, Pfahlberg A, et al. Outdoor work and skin cancer incidence: a registry-based study in Bavaria. Int Arch Occup Environ Health 2009;82:357-63.Mustieles V, Balogh RK, Axelstad M, et al. Benzophenone-3: comprehensive review of the toxicological and human evidence with meta-analysis of human biomonitoring studies. Environ Int 2023;173:107739.Schneider SL, Lim HW. Review of environmental effects of oxybenzone and other sunscreen active ingredients. J Am Acad Dermatol 2019;80(1):266-71.McMahon S. These 7 destinations are banning certain sunscreens. (accessed November 26, 2024).Kaur CD, Saraf S. In vitro sun protection factor determination of herbal oils used in cosmetics. Pharmacognosy Res 2010;2(1):22-5.Canadian Dermatology Association. Sunscreen FAQ. (accessed November 27, 2024).Nohynek GJ, Dufour EK. Nano-sized cosmetic formulations or solid nanoparticles in sunscreens: a risk to human health? Arch Toxicol 2012;86(7):1063-75.Gulson B, McCall M, Korsch M, et al. Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin. Toxicol Sci 2010;118(1):140-9.D’Orazio J, Jarrett S, Amaro-Ortiz A, et al. UV radiation and the skin. Int J Mol Sci 2013;14(6):12222-48.Lapides R, Saravi B, Mueller A, et al. Possible explanations for rising melanoma rates despite increased sunscreen use over the past several decades. Cancers 2023;15(24):5868.Barnes PW, Robson TM, Zepp RG, et al. Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system. Photochem Photobiol Sci 2023;22(5):1049-91.Baldermann C, Laschewski G, Groob JU. Impact of climate change on non-communicable diseases caused by altered UV radiation. J Health Monit 2023;8(Suppl 4):57-75.Autier P, Boniol M, Dore JF. Sunscreen use and increased duration of intentional sun exposure: still a burning issue. Int J Cancer 2007;121(1):1-5.Diffey B. Sunscreen isn’t enough. J Photochem Photobiol B 2001;64(2-3):105-8.McGill University. The sunscreen paradox: McGill University researchers warn of ‘false sense of security.’ (accessed November 27, 2024).American Academy of Dermatology. American Academy of Dermatology warns that homemade sunscreens are not proven to be effective and may leave users vulnerable to skin cancer. (accessed November 26, 2024).Harger B. Compounding opportunities for summer. (accessed November 26, 2024).Canadian Skin Cancer Foundation. What is skin cancer? (accessed November 26, 2024).