Don’t take our word for it. Here’s every fact on this site, with its evidence grade, its caveats, and a link to the source, so you can check us.
We start you on the strong ones: findings that have been replicated or come from one large, well-controlled study. Moderate and weak facts are here too, labeled for what they are. Use “Link to this fact” to share a single card.
Hidden ingredients / Review of other studies
FDA's voluntary cosmetic registration listed benzyl alcohol in only 322 formulations in 1998 and 511 products in 2006, far below its real use in moisturizers, shampoos, baby products, and deodorants, which the authors call widespread under-reporting.
Moderate evidence.
Caveats
The 322-formulation count for 1998 is now confirmed against the primary source: CIR's 2001 safety report (Nair 2001) reproduces the identical FDA VCRP count in its own Table 2, with a full 34-category breakdown (largest use hair dyes and colors, 130/1572; baby shampoos 5/21; baby lotions 3/53) — this is the exact table Jacob & Barron's figure traces to, not a secondhand citation. The 511-products-in-2006 figure remains an unpublished personal communication (postdates the 2001 report, so it cannot confirm or deny it). The same 2001 report separately documents that FDA stopped collecting concentration-of-use data after 1992, an independently CIR-acknowledged registry gap that supports treating VCRP counts as an incomplete picture of real use, distinct from the authors' own 'under-reporting' framing.
Hidden ingredients / Advocacy group testing
In a 2010 survey of more than 11,000 Canadian personal-care products with ingredient lists, 'fragrance' or 'parfum' was the most common ingredient of concern, listed on 56% of products and on about two-thirds of shampoos, soaps, and deodorants.
Moderate evidence: Self-selected volunteers read labels; product entries not de-duplicated; 2010 formulations; label count is a lower bound on fragranced products.
Hidden ingredients / Other evidence
A 1998 GC-MS survey of 71 European deodorants found 226 distinct fragrance and non-fragrance chemicals – more than ten times the 21 fragrance substances the same research group had specifically targeted and quantified in a companion study on the same products.
Moderate evidence: Single study, 1998 market snapshot (product formulations have changed since); no concentrations measured for any of the 226 chemicals, only presence/absence by product type.
Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact
Hidden ingredients / Other evidence
Methyl anthranilate, flagged by this 1998 GC-MS/SAR survey as an aromatic amine (a structural class linked to sensitization and other toxicity concerns), was found in 22 of 71 European deodorants tested, a chemical identity a fragrance label would not disclose since it is covered by the generic term 'parfum'.
Moderate evidence: Structural classification, not a clinical allergy finding for this specific compound in this paper; presence only, not concentration.
Source: Rastogi et al. 1998 (Contact Dermatitis 39:293), Contact Dermatitis Link to this fact
Hidden ingredients / Review of other studies
Fragrance in deodorants and antiperspirants often functions as a deliberate odor-masking ingredient at percent-level concentrations (e.g., linalool combined with dihydromyrcenol at 0.2-1% w/w, or a multi-fragrance blend of musk, skatole, lemon oil, lavender oil, jasmine, vanillin, benzoin, benzyl acetate, and menthol in one patented licorice-root deodorant), separate from and in addition to any anti-microbial active in the same product.
Moderate evidence.
Caveats
Review compiling cosmetics-industry patents and older formulation studies, not new experimental data; the specific listed formulations are patent examples, not necessarily current marketed products.
Source: Kanlayavattanakul & Lourith 2011, International Journal of Cosmetic Science Link to this fact
Hidden ingredients / Lab study (cells or chemistry)
In a lab test of 25 commercial underarm deodorants, 9 (36%) showed measurable estrogen-like activity in a human breast-cancer-cell assay, concentrated almost entirely in sprays (7 of 10) versus roll-ons (1 of 9) and sticks (1 of 6) from the same product lines.
Moderate evidence.
Caveats
Single lab, single 5-day cell-proliferation assay (E-Screen/MCF-7) per product; no second confirmatory assay, no dermal absorption or human data; the assay is a mixture 'sum parameter' that cannot identify which ingredient(s) drove any one product's result.
Hidden ingredients / Lab study (cells or chemistry)
Testing 62 individually purchased fragrance-related ingredients found in the deodorants, 8 were estrogenic in the same cell assay – including the musk HHCB/galaxolide and benzyl salicylate – at potencies the study describes as comparable to parabens, a preservative class with well-documented weak estrogenic activity.
Moderate evidence.
Caveats
Potencies were 100,000 to 100,000,000 times weaker than estradiol (EC50 3.08×10^-6 to 1.45×10^-4 M; EEF 2.34×10^-8 to 1.15×10^-6); a positive result in this cell assay does not establish that any dose reaches human tissue.
Hidden ingredients / Measured in people or real products
In a 2018 Korean government survey of 482 market deodorants, 18 of 26 screened fragrance allergens and 13 of 27 screened biocidal ingredients were actually detected in the products; some fragrance ingredients reached extreme concentrations in individual products, including benzyl benzoate at 142,344 mg/kg (about 14% of product weight) and thymol at 271,525 mg/kg (about 27% of product weight).
Moderate evidence: Single Korean-market survey (64-482 products depending on the ingredient panel); concentrations are maxima found in specific products, not typical or average levels.
Source: Kim et al. 2018, Science of The Total Environment Link to this fact
Hidden ingredients / Review of other studies
"Alum stone" deodorants are potassium alum (Al3K(SO4)2, 12H2O), which does contain aluminum, sometimes marketed under the name "potassium alum" or the misleading "double potassium sulfate," which omits the word aluminum entirely.
Moderate evidence: Single review's characterization of marketing language, not a systematic label survey.
Source: Martini 2020, Annales de Dermatologie et de Vénéréologie Link to this fact
Hidden ingredients / Measured in people or real products
Hormone-disrupting chemicals in household cleaners, synthetic detergents, fabric softeners, air fresheners, and deodorants are almost always added as fragrance or preservative, not as the product's main ingredient, so their presence rarely shows up as a headline ingredient a shopper would notice.
Moderate evidence: Based on a database of listed ingredients matched to EPA hazard flags, not chemical measurement of the actual products; a single country's product registry (South Korea, 2020).
Source: Lee & Ji 2022, Ecotoxicology and Environmental Safety Link to this fact
Hidden ingredients / Measured in people or real products
All 17 everyday product perfumes (shampoos, baby bath, lotions, deodorants) contained at least one of the fragrance-mix allergens by GC-MS, about 2.6-2.8 on average; geraniol was in 12 of 17.
Moderate evidence: Single manufacturer's lower-priced perfumes, 1990s Denmark; oak moss not analyzed; concentrations are in the perfume, not the finished product.
Source: Johansen 1997, Contact Dermatitis Link to this fact
Hidden ingredients / Other evidence
Limonene and beta-pinene scent terpenes were measurable in every perfume, deodorant and cleaning liquid tested (about 0.1-0.3% and 0.04-0.65% of product weight), even though labels only say 'fragrance' or, for the cleaners, name limonene.
Moderate evidence.
Caveats
Six products; GC-MS of three terpenes only, so other scent chemicals are unmeasured; alpha-pinene was below the detection range. The abstract's beta-pinene range (0.4-0.7%) differs from Table 1 (0.04-0.65%).
Information, not medical advice. See also: myths we won’t tell you.