Contact Allergens in “PPD-Free” Hair Dyes
Bibliographic record
Abstract
Abstract: Background: Hair dyes are a commonly used cosmetic product and an important cause of allergic contact dermatitis (ACD). Primary hair dye agents, paraphenylenediamine (PPD) and other aromatic amines, are potent contact sensitizers. Despite some hair dyes being advertised as all natural or allergen-free, patients still present with hair dye contact allergy following the use of these products. We hypothesized that these products may contain cross-reactive ingredients not tested on standard series or undisclosed ingredients such as trace amounts of the allergens. Objective: We aimed to test hair dyes marketed and sold in the United States as “PPD-free” for the presence and quantity of common hair dye allergens and ingredients, including p-phenylenediamine, m-aminophenol, p-aminophenol, toluene-2,5-diamine sulfate, 2-nitro-p-phenylenediamine, and 2-hydroxy-1,4-naphthoquinone. Methods: We tested best-selling hair dyes advertised as “PPD-free” for common allergens through high-performance liquid chromatography coupled to high-resolution mass spectrometry. Results: In 7 out of 51 hair dye products, we detected a compound that was not present on the ingredient list. Five products contained PPD despite no mention of PPD on the ingredient list and 4 being labeled “PPD-free.” One of these products contained PPD levels higher than 2% by weight, while the rest contained trace levels. Conclusions: These findings may help guide dermatologists in counseling patients with ACD about the importance of performing allergy alert testing before the use of a new hair dye product, regardless of how it is commercially advertised or labeled.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".