Quantification of Lawsone and p-Phenylenediamine in Natural Henna Products for Hair Colouring Available in Poland.

Summary

Validated dual HPLC-UV methods showed that only about 60% of tested henna cosmetics contained ≥0.5% lawsone, while up to 36% harbored p-phenylenediamine (1–9%), with incomplete labeling. Findings highlight widespread adulteration and regulatory gaps in online-distributed henna products.

Key Findings

• Approximately 60% of tested henna cosmetics qualified as natural products with ≥0.5% lawsone (range 0.5–1.0%).
• Up to 36% of samples contained p-phenylenediamine at 1–9%, a strong contact allergen.
• Only a subset of PPD-containing products were properly labeled, indicating regulatory and labeling gaps.

Clinical Implications

Clinicians should counsel patients on PPD risks in henna, consider patch testing in dermatitis, and advise sourcing from transparent suppliers; regulators may need targeted surveillance of online products.

Limitations

• Sampling frame and number of products were not detailed, limiting generalizability
• Study focused on products available in Poland, many purchased online

Future Directions

Expand surveillance to broader markets with randomized sampling, link product analytics to clinical allergy incidence, and support harmonized labeling and enforcement.