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
In a 2015 survey of 187 US pediatric personal-care products marketed as hypoallergenic, dermatologist-recommended, fragrance-free, or paraben-free, 89% (167/187) contained at least one contact allergen from the standard NACDG screening tray, with a mean of 2.4 allergens per product.
Strong evidence.
Caveats
Single-metro US convenience sample (six unnamed Redlands, CA retailers, 2013), label-based (no chemical verification, no concentrations), and allergen matching by an unaudited custom algorithm; the four marketing-term categories overlap (a product can carry more than one), so subgroup percentages are not independent comparisons.
Source: Hamann 2015, Journal of Allergy and Clinical Immunology Link to this fact
Skin allergy / Measured in people or real products
In a clinical study of 658 hand-eczema patients across 3 European centers, 67 (10.2%) reacted on patch testing to at least one fragrance chemical selected because it is common in household cleaning and personal-care products used on the hands.
Strong evidence: Clinic-referred hand-eczema population (3 tertiary centers), not a random sample of the general public.
Source: Heydorn 2003, Contact Dermatitis Industry-funded Link to this fact
Information, not medical advice. See also: myths we won’t tell you.