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.
Skin allergy / Measured in people or real products
The two commonest fragrance allergens on Danish children's cosmetics, limonene (22% of fragranced products) and linalool (18%), are not in the standard European patch test series; they become strong allergens when they oxidize in air.
Moderate evidence: Frequencies are label presence; oxidation not measured in these products (relayed from hydroperoxide literature); some clinics now add the hydroperoxides to their baseline.
Skin allergy / Other evidence
In 23,846 people patch tested at a London skin-allergy clinic (1984-1998), allergy to the standard fragrance mix was uncommon in children and teenagers (about 3%) but reached about 14% in women in their 60s and men in their 70s.
Moderate evidence: One clinic's referred patients, cross-sectional by age; not general-population rates, and not a follow-up of individuals.
Source: Buckley 2003, British Journal of Dermatology Link to this fact
Skin allergy / Other evidence
Children react to disperse dyes too: North American data found 2.1% of children vs 2.4% of adults positive to Blue 106, and a meta-analysis found only Blue 124 above 1% in children.
Moderate evidence: Referred children only, small studies; rates varied 0.3% to 4.0% across studies.
Source: Malinauskiene 2013, Contact Dermatitis Link to this fact
Skin allergy / Review of other studies
Aluminum skin allergy is uncommon in adults but not rare in children: in a Swedish clinic series, 0.9% of 5,448 adults and 5.1% of 196 children patch-tested positive to aluminum salts, and a meta-analysis found 0.4% of adults and 5.6% of children.
Moderate evidence.
Caveats
Narrative review relaying Swedish and Danish clinic data from related groups; tested patients are dermatitis patients or children referred for suspected allergy, not the general population.
Source: Novack 2022, Cutis Link to this fact
Skin allergy / Review of other studies
A small share of children develop persistent itchy lumps at the injection site after aluminum-containing vaccines (under 1% in large studies of up to about 76,000 children); about 77-95% of them test allergic to aluminum, and the lumps usually fade over a median of 18-49 months.
Moderate evidence: Relayed from two Swedish cohorts, one tied to a single manufacturer's vaccines; this is not a vaccine safety study.
Source: Novack 2022, Cutis Link to this fact
Skin allergy / Other evidence
A 2012-13 Danish EPA screen of 31 mostly polyester garments (about 10 for children) found none of 23 allergenic disperse dyes, after a second LC-MS method showed eight first-pass Disperse Blue 124 and Yellow 49 hits were false positives.
Moderate evidence: Small, deliberately targeted sample from Danish shops; 31 garments and 23 dyes; the interfering compound was never identified; no certified garments tested.
Source: Danish EPA 2014, Survey of Chemical Substances in Consumer Products No. 129 Link to this fact
Skin allergy / Other evidence
In four- and two-week home-use tests, 175 adults and children with dry, eczema-prone or atopic skin used behentrimonium chloride body lotions with no clinically assessed reactions; a handful of brief itch or sting reports (five people) were the only complaints.
Moderate evidence: Short (2-4 weeks), small, specific formulations from one company, no unexposed or independent comparator in most arms; manufacturer-run.
Source: Cameron 2013, Toxicology in Vitro Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.