10 Compounds Linked to Cancer That Can Turn Up in Your Skincare
The full guide
What I learned in 20 years of cancer diagnostics, and what the evidence actually says.
Hana Maatugh
Biomedical Scientist · MSc Molecular Biology · Skincare Formulator
Knowledge, not fear.
For over twenty years I worked in cellular pathology, the part of the hospital where cancer is diagnosed. I have looked at thousands of cells under the microscope. I have extracted DNA. I have seen what the end of the story looks like.
Now I formulate skincare, and I read ingredient lists the way I used to read slides: slowly, and with the evidence open next to me.
I did not write this guide to scare you. Every compound here has a real classification from the International Agency for Research on Cancer (IARC), a real route into cosmetics, and a published reference you can check yourself. Where the evidence is weak, or reassuring, I have said so.
Hazard is not the same as risk.
IARC tells us whether something can cause cancer. It does not tell us how likely it is at the dose you are exposed to. Processed meat and sunlight are both Group 1. What matters is how much, how often, and by which route: on the skin, breathed in, or swallowed.
- Group 1: carcinogenic to humans.
- Group 2A: probably carcinogenic.
- Group 2B: possibly carcinogenic.
- Group 3: not classifiable.
01. Formaldehyde and formaldehyde releasers
IARC Group 1 · Carcinogenic to humans
What it is
A preservative gas. In cosmetics it is rarely added directly. Instead, “releaser” preservatives slowly give off small amounts of formaldehyde in water based products to stop microbes growing.
Where it can hide
Shampoos, body washes, some creams and lotions, nail products, and heated hair smoothing treatments (the “keratin” or Brazilian blow dry type), where the heat turns it into a vapour you breathe in.
What the evidence says
IARC classifies formaldehyde as Group 1, based mainly on nasopharyngeal cancer and myeloid leukaemia in people who inhale it at work [1]. The level of risk from small amounts in a rinse off product on your skin has not been established. It is, however, one of the most common causes of allergic contact dermatitis.
UK position
Releasers are still permitted within set limits. From 15 August 2026, UK products that release more than 0.001% formaldehyde must carry the warning “releases formaldehyde”, bringing the UK in line with the EU [2].
On the label
DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, quaternium 15, bronopol, sodium hydroxymethylglycinate, methenamine.
My take: This one is easy to avoid, and if your skin barrier is already fragile I would avoid it anyway. Be most careful with heated hair treatments in small, poorly ventilated rooms.
02. Benzene
IARC Group 1 · Carcinogenic to humans
What it is
A solvent that is never meant to be in your skincare. When it turns up, it is a contaminant, coming from propellants, raw materials or the breakdown of certain ingredients.
Where it can hide
Some aerosol sunscreens and after sun sprays, aerosol dry shampoos, and some benzoyl peroxide acne products, where benzene can form when the product gets warm.
What the evidence says
Benzene causes acute myeloid leukaemia (IARC Group 1) [3]. In 2021 an independent lab reported benzene in about a quarter of the sunscreen batches it tested, and five Neutrogena and Aveeno aerosol sunscreens were recalled [4]. Aerosol dry shampoo recalls followed. In 2024 researchers showed benzoyl peroxide can break down to benzene at high storage temperatures [5]. When the US FDA tested 95 benzoyl peroxide products in 2025, 6 had raised levels and were recalled, and the FDA said the resulting cancer risk was “very low”, even with daily use for decades [6].
UK position
Benzene is prohibited as a cosmetic ingredient. Contamination is the manufacturer’s responsibility to test for and control.
On the label
You will never see it on an ingredient list. Watch the format (aerosols) and how you store things.
My take: Choose lotions and creams over aerosol sprays where you can, never spray near your face, and keep products out of hot cars and sunny windowsills.
03. PFAS, the “forever chemicals”
IARC Group 1 (PFOA) · PFOS: Group 2B
What it is
A large family of fluorinated chemicals that repel water and oil. They are called forever chemicals because they barely break down in the body or the environment.
Where it can hide
Long wear and waterproof makeup: waterproof mascara, long lasting liquid lipstick, some foundations and pressed powders, used for water resistance and a smooth, silky feel.
What the evidence says
In 2023 IARC classified PFOA as carcinogenic to humans (Group 1) and PFOS as possibly carcinogenic (Group 2B) [7]. A 2021 study screened 231 cosmetics sold in North America and found high fluorine in 82% of waterproof mascaras, 63% of foundations and 62% of liquid lipsticks. Of 29 products analysed in depth, each contained between 4 and 13 different PFAS, and only one listed them on the label [8]. Most PFAS found in cosmetics are not PFOA itself, but some can break down into related long chain compounds.
UK position
There is currently no UK ban specific to PFAS in cosmetics. France banned PFAS in cosmetics from 1 January 2026 [9].
On the label
PTFE (polytetrafluoroethylene), perfluorodecalin, any ingredient containing “perfluoro”, “polyfluoro” or “fluoro”.
My take: Scan for the word “fluoro”. If a product promises to survive a swimming pool, it is worth a second look.
04. Asbestos in contaminated talc
Asbestos: IARC Group 1 · Talc: Group 2A (2024)
What it is
Talc is a soft mineral powder. It is mined, and talc deposits can sit right next to asbestos, so poorly sourced or poorly tested talc can be contaminated.
Where it can hide
Loose and pressed powders, eyeshadow, blusher, bronzer, body and baby powders, some dry shampoos.
What the evidence says
Asbestos is a proven cause of mesothelioma and of lung and ovarian cancer (Group 1) [1]. In July 2024 IARC classified talc itself as “probably carcinogenic” (Group 2A), based on limited evidence in humans (mainly ovarian cancer with genital use), sufficient evidence in animals and strong mechanistic evidence. IARC noted that asbestos contamination could not be ruled out in the human studies [10]. US FDA testing in 2019 and 2020 found asbestos in several talc cosmetics and led to recalls. The FDA proposed compulsory asbestos testing in 2024, then withdrew it in November 2025 with the stated aim of reissuing it [11].
UK position
Asbestos is prohibited. Talc is permitted and must be free of asbestos.
On the label
Talc (INCI: Talc).
My take: I would not use talc on the genital area and I would not breathe in loose powders. Talc free powders based on starches or silica are widely available.
05. Coal tar
IARC Group 1 · Coal tar and coal tar pitch
What it is
A thick by product of turning coal into coke and gas. It has been used for over a century to calm scaly skin.
Where it can hide
In the UK, coal tar is not allowed in cosmetics. You will find it in licensed medicines for psoriasis, dandruff and eczema, such as some medicated shampoos and ointments. Some imported or overseas shampoos also contain it.
What the evidence says
Occupational exposure to coal tar and its fumes causes skin and lung cancer (Group 1) [1]. But the dose and route matter. A study of over 13,000 patients treated with coal tar for psoriasis and eczema found no increased risk of skin cancer or other cancers [12].
UK position
Prohibited in cosmetic products. Permitted as a licensed medicine, used under guidance.
On the label
Coal tar, pix carbonis, crude coal tar. Note: modern synthetic colourants are sometimes loosely called “coal tar dyes”. That is a different topic.
My take: This is where nuance matters. If your GP or dermatologist has prescribed a coal tar product, do not stop it because of a reel. Talk to them. What I would avoid is unlicensed imported products.
06. 1,4 dioxane
IARC Group 2B · Possibly carcinogenic to humans
What it is
A manufacturing residue, not an ingredient. It forms during ethoxylation, the process used to make many gentle foaming agents and emulsifiers.
Where it can hide
Shampoos, body washes, bubble baths, liquid soaps and some creams.
What the evidence says
1,4 dioxane causes liver and nasal tumours in animals, which is why IARC lists it as possibly carcinogenic to humans (Group 2B) [13]. The EU Scientific Committee on Consumer Safety considers trace levels up to 10 ppm in a finished product to be safe [14]. New York State now legally caps it at 10 ppm in cosmetics. Manufacturers can strip it out with vacuum processing, but not all do.
UK position
Prohibited as an ingredient. Unavoidable traces are allowed only if the product is still judged safe.
On the label
Sodium laureth sulfate, PEG compounds, polysorbates, ceteareth, and many ingredients ending in “eth” or “oxynol”.
My take: Ethoxylated does not automatically mean contaminated. A good brand will tell you whether they test their raw materials. Ask.
07. Nitrosamines (and DEA)
IARC Group 2B · NDELA and diethanolamine
What it is
Nitrosamines are not added on purpose. They form inside a product when certain amine ingredients react with nitrosating agents, such as some preservatives.
Where it can hide
Foaming cleansers, shampoos, body washes, some creams and some makeup.
What the evidence says
N nitrosodiethanolamine (NDELA) and diethanolamine (DEA) are both classified as possibly carcinogenic to humans (Group 2B), largely from animal studies [15]. Nitrosamines as a family are among the most potent carcinogens known in animal testing.
UK position
Tightly controlled. Amine ingredients such as TEA and certain amides are restricted, must not be used with nitrosating systems, and raw materials must be kept below 50 micrograms of nitrosamines per kilogram [16].
On the label
Cocamide DEA, lauramide DEA, TEA (triethanolamine), MEA. The red flag combination is one of these with bronopol.
My take: Regulated products keep nitrosamines very low. The combination of an amine and a nitrosating preservative is what I look for, and what I avoid in my own formulas.
08. Lead
IARC Group 2A · Inorganic lead compounds
What it is
A heavy metal. It has no safe level in the body and is prohibited in UK cosmetics, but it still reaches homes through imported products.
Where it can hide
Traditional kohl, kajal and surma, where lead sulphide can make up a large part of the powder, and some imported lipsticks and eye products bought online or abroad.
What the evidence says
Inorganic lead compounds are probably carcinogenic to humans (Group 2A) [17]. Even more serious is lead’s effect on the developing brain, which is why applying kohl to babies’ and children’s eyes is a particular concern for public health agencies [18].
UK position
Prohibited in cosmetics. Trading Standards regularly remove non compliant eye products from sale.
On the label
Often not listed at all. Be wary of products with no full ingredient list, no UK or EU responsible person, or labels only in another language.
My take: Kohl carries deep cultural meaning in many families. Choose one sold by a UK compliant brand, and please do not use traditional surma on babies.
09. Titanium dioxide, when inhaled
IARC Group 2B · By inhalation only
What it is
A white mineral used as a colour and as a UV filter in mineral sunscreens.
Where it can hide
Loose powders, setting sprays, and spray sunscreens, where fine particles can be breathed in.
What the evidence says
IARC lists titanium dioxide as possibly carcinogenic (Group 2B) because of lung tumours in rats that inhaled high levels of dust [19]. It does not meaningfully get through healthy, intact skin. In the EU, a classification of the powder form as a suspected inhalation carcinogen was annulled by the General Court in 2022, and that ruling was upheld by the Court of Justice in August 2025 [20].
UK position
Permitted as a colourant and UV filter, with restrictions on uses that could lead to inhalation.
On the label
Titanium dioxide, CI 77891.
My take: This one is about the format, not the ingredient. Mineral sunscreen creams with titanium dioxide or zinc oxide remain one of the best supported ways to protect your skin. Just do not breathe in sprays and loose powders.
10. Chemical hair straighteners and permanent dyes
Hairdressers: IARC 2A · Personal use: not classifiable
What it is
Not a single compound, but a group of products with a complex mix of chemicals, including formaldehyde releasers, aromatic amines and hormone active ingredients.
Where it can hide
Relaxers, perms and straightening creams; permanent (oxidative) hair colour.
What the evidence says
In the US Sister Study of almost 34,000 women, frequent straightener users (more than four times a year) had about 2.5 times the risk of uterine cancer compared with never users. By age 70 the estimated risk was 4.05% versus 1.64% [21]. In the same cohort, permanent dye use was linked to a 9% higher breast cancer risk overall and 45% higher in Black women [22]. A larger study of over 117,000 US nurses did not find higher risk for most cancers with personal dye use [23]. IARC classifies occupational exposure as a hairdresser as probably carcinogenic (2A), but personal use as not classifiable [24].
UK position
Many hair dye ingredients have been banned in the UK and EU following safety reviews. The products that remain are permitted within limits.
On the label
Look for formaldehyde releasers (see 01) in straighteners, and for “PPD” (p phenylenediamine) or “toluene 2,5 diamine” in permanent colour.
My take: The evidence is observational and the exact culprit is unknown, but the signal for frequent straightener use is strong enough that I would space treatments out, and protect your scalp.
What I did not put on this list, and why.
Good science means saying “the evidence does not support that” as often as it means raising a flag.
Parabens. Not classified as carcinogenic by IARC. Finding parabens in breast tissue showed they were present, not that they caused cancer [25]. The EU safety committee considers methyl and ethylparaben safe at permitted levels. I leave them out of my own formulas for other reasons, but I will not call them carcinogens.
Aluminium in antiperspirants. Cancer Research UK states there is no good evidence that antiperspirants or deodorants cause breast cancer [26].
Sodium lauryl sulfate (SLS). An irritant that can strip a fragile barrier, so I avoid it for that reason. It is not a carcinogen. It often gets confused with sodium laureth sulfate, which is where the 1,4 dioxane question comes from.
Mineral oil. Untreated or mildly treated mineral oils are Group 1. Highly refined cosmetic and pharmaceutical grade mineral oil is not classified as a carcinogen. What your skin thinks of it is a separate conversation.
Six habits that lower your exposure.
- Read the full ingredient list, not the front of the pack. “Natural” and “clean” are marketing words, not safety standards.
- Search for three words: “fluoro”, “DEA” and the formaldehyde releasers listed in section 01.
- Prefer creams to aerosols, and never spray near your face.
- Store products cool, away from sunny windowsills and hot cars.
- Buy from UK compliant sellers. Every cosmetic sold here must name a UK responsible person and carry a full ingredient list.
- Fewer products, fewer exposures. Your skin does not need a ten step routine.
Check my sources.
- IARC Monographs Volume 100F. Chemical agents and related occupations (formaldehyde, coal tar pitch, asbestos). Lyon: IARC; 2012.
- UK Government. Amendment to the UK Cosmetics Regulation lowering the “releases formaldehyde” labelling threshold to 0.001%, applying from 15 August 2026; aligned with Commission Regulation (EU) 2022/1181.
- IARC Monographs Volume 120. Benzene. Lyon: IARC; 2018.
- Valisure. Citizen petition on benzene contamination in sunscreen and after sun products. May 2021; Johnson & Johnson voluntary recall of five aerosol sunscreens, July 2021.
- Kucab H, et al. Benzoyl peroxide drug products form benzene. Environmental Health Perspectives. 2024;132(3):037702.
- US FDA. Limited number of voluntary recalls initiated after FDA testing of acne products for benzene. 11 March 2025.
- Zahm S, et al. Carcinogenicity of perfluorooctanoic acid and perfluorooctanesulfonic acid. Lancet Oncology. 2024;25(1):16-17. (IARC Monographs Volume 135.)
- Whitehead HD, et al. Fluorinated compounds in North American cosmetics. Environmental Science & Technology Letters. 2021;8(7):538-544.
- French Republic. Law of 27 February 2025 on protecting the population from PFAS risks; cosmetics provisions in force 1 January 2026.
- IARC Monographs Volume 136. Talc and acrylonitrile. Lancet Oncology summary, July 2024.
- US FDA. Testing methods for detecting and identifying asbestos in talc containing cosmetic products; withdrawal. Federal Register, 28 November 2025.
- Roelofzen JH, et al. No increased risk of cancer after coal tar treatment in patients with psoriasis or eczema. Journal of Investigative Dermatology. 2010;130(4):953-961.
- IARC Monographs Volume 71. Re-evaluation of some organic chemicals (1,4 dioxane). Lyon: IARC; 1999.
- Scientific Committee on Consumer Safety. Opinion on the safety of the presence of 1,4 dioxane as traces in cosmetic products. SCCS/1570/15; 2015.
- IARC Monographs Volume 17 and Supplement 7 (N nitrosodiethanolamine); Volume 101 (diethanolamine, coconut oil diethanolamine condensate). Lyon: IARC.
- UK Cosmetic Products Regulation (retained Regulation (EC) No 1223/2009), Annex III entries on alkanolamines and alkanolamides.
- IARC Monographs Volume 87. Inorganic and organic lead compounds. Lyon: IARC; 2006.
- US FDA. Kohl, kajal, al kahal, surma, tiro, tozali or kwalli: by any name, beware of lead. Consumer guidance.
- IARC Monographs Volume 93. Carbon black, titanium dioxide and talc. Lyon: IARC; 2010.
- Court of Justice of the European Union. Joined appeals on Commission Delegated Regulation (EU) 2020/217 (titanium dioxide). Judgment of 1 August 2025.
- Chang CJ, et al. Use of straighteners and other hair products and incident uterine cancer. Journal of the National Cancer Institute. 2022;114(12):1636-1645.
- Eberle CE, et al. Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women. International Journal of Cancer. 2020;147(2):383-391.
- Zhang Y, et al. Personal use of permanent hair dyes and cancer risk and mortality in US women: prospective cohort study. BMJ. 2020;370:m2942.
- IARC Monographs Volume 99. Some aromatic amines, organic dyes and related exposures. Lyon: IARC; 2010.
- Darbre PD, et al. Concentrations of parabens in human breast tumours. Journal of Applied Toxicology. 2004;24(1):5-13.
- Cancer Research UK. Can antiperspirants or deodorants cause breast cancer? Cancer myths and controversies.
This guide is for education only and is not medical advice. It does not replace advice from your GP, dermatologist or pharmacist. Please do not stop a prescribed treatment without speaking to them first. Information correct at the time of writing, September 2026.
Comfortable skin is a need, not a want.
Questions about your own products? Send me a DM on Instagram and I will do my best to help. Hana
