Key Takeaways
Why Some Cosmetic Ingredients Deserve a Second Look
Personal care products — from shampoo and moisturiser to sunscreen and deodorant — are applied daily, often across multiple body sites. Because skin is a functional barrier rather than an impermeable wall, some compounds in these products can be absorbed, at least in small amounts. That reality has pushed ingredient safety increasingly into public health conversations.
The US Food and Drug Administration (FDA) regulates cosmetics, but unlike pharmaceuticals, cosmetic ingredients generally do not require pre-market safety approval. Responsibility falls largely on manufacturers. This regulatory gap is why consumers, researchers, and advocacy groups pay close attention to certain ingredient classes — not to create alarm, but to make more informed choices.
This reference list covers commonly scrutinised ingredients: what they are, what current evidence suggests, and what you might reasonably consider. It is general health information, not medical advice. If you have specific concerns, speak with a dermatologist or healthcare provider. For help decoding labels before diving in, see our guide on reading a cosmetic ingredient list without a chemistry degree.
Parabens
Parabens (methylparaben, propylparaben, butylparaben, and others) are synthetic preservatives used widely in cosmetics to prevent microbial growth and extend shelf life. They are among the most studied cosmetic ingredients.
Research has detected parabens in human urine, blood, and breast tissue, indicating absorption occurs. Some parabens exhibit weak estrogenic activity in laboratory settings — meaning they can weakly mimic estrogen. However, established health agencies including the European Scientific Committee on Consumer Safety have evaluated certain parabens (notably methylparaben and ethylparaben) as safe at regulated concentrations for individual use. Longer-chain parabens such as butylparaben and propylparaben face more restriction, particularly in leave-on products in the EU.
In the US, parabens remain permitted with no explicit concentration caps. If reducing exposure is a priority for you, checking for paraben-free formulations is straightforward, as labelling tends to call them out clearly.
Some parabens exhibit weak estrogenic activity in lab settings, though regulatory agencies consider short-chain variants safe at typical use levels.
Phthalates
Phthalates are a class of plasticising chemicals used in cosmetics primarily as fragrance carriers and film-formers. Diethyl phthalate (DEP) is the most common in personal care. Others — like DEHP, DBP, and BBP — are more restricted and found less often in cosmetics, though they appear in plastics and other consumer products.
Phthalates are endocrine-disrupting chemicals (EDCs), meaning they may interfere with hormone signalling. Human epidemiological studies have associated urinary phthalate metabolites with reproductive and developmental outcomes, though establishing direct causation from cosmetic use specifically remains difficult given widespread environmental exposure from multiple sources.
Because phthalates often appear under the umbrella term "fragrance" or "parfum" on ingredient labels — and companies are not required to disclose individual fragrance components — identifying them without third-party databases can be challenging. Fragrance-free or fully disclosed-fragrance formulas reduce phthalate uncertainty.
Phthalates often hide under the term 'fragrance' on labels, making third-party ingredient databases a useful transparency tool.
Formaldehyde and Formaldehyde-Releasing Preservatives
Formaldehyde is a known human carcinogen. It is not always added directly to cosmetics, but a family of preservatives — including DMDM hydantoin, quaternium-15, imidazolidinyl urea, and diazolidinyl urea — release small amounts of formaldehyde over time to prevent microbial contamination.
Skin sensitisation and allergic contact dermatitis are the most commonly reported concerns at cosmetic use levels. The International Agency for Research on Cancer (IARC) classifies formaldehyde as a Group 1 carcinogen based primarily on occupational inhalation data (e.g., salon workers using certain hair-straightening treatments), rather than typical topical cosmetic exposure.
Regulatory limits exist in the EU; the US has no set cosmetic concentration limits for these preservatives, though the FDA has issued warnings related to specific hair-straightening product categories. People with known formaldehyde sensitivity should scan INCI names carefully.
Formaldehyde-releasing preservatives are most concerning for individuals with skin sensitisation or in occupational high-exposure settings.
Synthetic Musks
Synthetic musks are fragrance compounds used in perfumes, lotions, and hair products to provide long-lasting scent. They fall into two main chemical families: polycyclic musks (such as galaxolide and tonalide) and nitro musks (some of which, like musk ambrette, have been banned or restricted due to toxicity concerns).
Research has found some synthetic musks bioaccumulate in human fatty tissue and breast milk, and laboratory studies have suggested potential endocrine-disrupting properties for certain compounds. Human health evidence remains limited, but their environmental persistence has raised broader sustainability concerns.
Choosing products with transparent fragrance disclosure or certified natural musk alternatives (like ambrette seed) is one option for those seeking to reduce exposure, though "natural" is not synonymous with risk-free. Our article on natural beauty myths that skin scientists want you to stop believing addresses this nuance directly.
Some synthetic musks bioaccumulate in human tissue — a concern distinct from immediate toxicity that informs broader low-toxin thinking.
Oxybenzone and Chemical UV Filters
Oxybenzone (benzophenone-3) is a chemical UV filter found in many sunscreens. It absorbs UVA and UVB radiation effectively. However, studies have detected oxybenzone in blood, urine, and breast milk after topical application, prompting an FDA review that requested additional safety data from manufacturers.
Proposed concerns include potential hormonal activity and skin sensitisation. The FDA currently classifies oxybenzone as a category III ingredient — meaning existing safety data are insufficient to classify it as GRAS/SAFE (generally recognized as safe and effective) without further study. It has not been banned. The agency has recommended continued sunscreen use given that UV protection's skin cancer prevention benefit is well established.
Mineral UV filters — zinc oxide and titanium dioxide — are the two ingredients the FDA has classified as GRASE. They work by physically scattering UV light and are generally well-tolerated, including for sensitive skin. If you prefer to avoid chemical filters, mineral-based options are widely available and clinically effective.
The FDA has not classified oxybenzone as safe or unsafe pending further data — mineral sunscreens offer a well-established alternative.
1,4-Dioxane (a Contaminant, Not an Added Ingredient)
Unlike the others on this list, 1,4-dioxane is not intentionally added to cosmetics. It is a byproduct of a manufacturing process called ethoxylation — used to make ingredients gentler and more soluble. Common ethoxylated ingredients include sodium laureth sulfate (SLES), PEG compounds, and certain emulsifiers identified by the prefixes PEG-, -eth, or -oxynol.
The International Agency for Research on Cancer classifies 1,4-dioxane as a possible human carcinogen (Group 2B). Because it is a contaminant rather than a listed ingredient, it will not appear on any label. Concentration varies by product and manufacturer. The FDA monitors levels in cosmetics and has encouraged industry to reduce contamination through purification steps, though there are currently no mandatory US limits specific to cosmetics.
Looking for products certified by organisations that test for contaminant levels, or choosing formulas that avoid ethoxylated surfactants entirely, are ways some consumers manage this uncertainty.
1,4-Dioxane won't appear on any label because it's a manufacturing byproduct — not a listed ingredient — making third-party testing key.
Putting the Evidence in Perspective
Scrutiny of an ingredient does not automatically mean it is harmful at typical cosmetic use levels. Science works in gradations — exposure duration, concentration, individual biology, and the combination of products used simultaneously all matter. Someone applying a trace-level preservative in a rinse-off shampoo faces a very different exposure scenario than one using a leave-on product daily for years.
Start With Leave-On, High-Contact Products
When evaluating your routine, prioritise products that stay on your skin the longest and cover the most surface area — body lotion, facial moisturiser, and deodorant — before targeting rinse-off products like shampoo or body wash. Absorption potential is meaningfully higher with leave-on formulas. Swapping one or two high-use products at a time makes change more manageable and helps you track how your skin responds.
If you want to take action, a gradual approach is most sustainable. Prioritise leave-on products used on large skin areas — body lotions, facial moisturisers, and deodorants — over rinse-off products, since absorption potential is generally higher. Our article on starting a low-toxin beauty routine without overhauling everything at once offers a practical framework for that process. For a broader periodic review of your entire routine, the annual natural beauty routine audit is a useful structured checklist.
This article is for general informational and educational purposes only and does not constitute medical advice. Consult a qualified healthcare professional for personalised guidance regarding any health concerns related to personal care ingredients.