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.
Health effects / Other evidence
The study's authors calculated that PPD loads of 22-939 nmol per hand (about 0.06-2.29 nmol/cm2 averaged over a 410 cm2 hand) exceed a calculated acceptable non-sensitizing area dose of 0.57 nmol/cm2 but are below experimental sensitization (9.3 nmol/cm2 NOEL) and elicitation (28 nmol/cm2) thresholds, and they argue repeated daily exposure may still be enough to sensitize or elicit allergy.
Weak evidence: Authors' extrapolation from hand averages; no sensitization outcomes were measured; real dose is unevenly distributed and likely higher in places.
Source: Lind et al. 2005, The Annals of Occupational Hygiene Link to this fact
Health effects / Review of other studies
Dermatologists judge that the allergy seen in a small proportion of children given aluminum-containing vaccines does not outweigh the benefit of vaccination for almost all children.
Weak evidence: Authors' opinion citing FDA and CDC positions; the paper presents no benefit-risk analysis of its own.
Source: Novack 2022, Cutis Link to this fact
Health effects / Government agency
A Danish allergy research center (NARC) commissioned a model that puts the lifetime cost of one average fragrance allergy case at about 182,000 DKK (about 24,000 EUR).
Weak evidence.
Caveats
A cost model built on stated assumptions (expert case splits, 5.6 sick days, a willingness-to-pay of 9,700 DKK per year borrowed from atopic and contact dermatitis), not measured patient costs. The report is not peer reviewed. Discounted over a 50-year horizon.
Source: COWI 2019 Link to this fact
Health effects / Government agency
A Danish model estimates fragrance allergy costs about 1.5 billion DKK a year nationally, for roughly 150,000 adults with symptoms.
Weak evidence.
Caveats
Modeled figure. The 150,000 is a steady-state output of the model's incidence and 4.4% annual decline assumptions, and is about 3.3% of Danish adults. The report's abstract calls it a 5% prevalence, which is the sensitized share, not the symptomatic one.
Source: COWI 2019 Link to this fact
Health effects / Government agency
A model extrapolated from Danish unit costs puts the annual EU28 cost of fragrance allergy at 11 to 16.4 billion EUR.
Weak evidence: Extrapolation, not an EU measurement. It assumes 4% to 6% of the EU population is sensitized, the Danish case mix everywhere, and a 30% price-level discount.
Source: COWI 2019 Link to this fact
Health effects / Government agency
In the model, about 43% of the lifetime cost of a fragrance allergy case is valued quality-of-life loss, while the public health system pays only about 3%.
Weak evidence.
Caveats
The 43% is a willingness-to-pay value (9,700 DKK per year after deducting private costs) borrowed from atopic and contact dermatitis studies; no fragrance-allergy willingness-to-pay study was found. The 3% is the public share of direct costs in the model.
Source: COWI 2019 Link to this fact
Health effects / Government agency
The model estimates about 8,500 new fragrance allergy cases a year in Denmark, of which about 3,750 are diagnosed by a dermatologist.
Weak evidence.
Caveats
Derived, not counted. 3,750 = 25,000 patch-tested patients a year x 15% positive, with 10% of those referred to hospital. The 8,523 total is 3,750 divided by 0.44, a hand-eczema referral ratio from a different study. Only the dermatologist and hospital endpoints are actually diagnosed.
Source: COWI 2019 Link to this fact
Health effects / Other evidence
In rosacea patients, allergy to the antibiotics gentamicin (8%, 6/75) and framycetin (5.3%, 4/76) was far above the under-0.5% estimated for the general population, possibly from eye treatment of rosacea symptoms.
Weak evidence: Small sample, wide CIs (gentamicin 3.0-16.6%); the eye-drop source is the authors' hypothesis, untested; population figure is an indirect estimate.
Information, not medical advice. See also: myths we won’t tell you.