Using the principle of data curation, American and German scientists succeeded in gaining new insights into the potential and weaknesses of using data from 2,277 test results on allergic contact dermatitis (HPPT) for 1,366 test substances. On this basis, the researchers derived important suggestions for improvement.

Since the 1940s, patch tests have been performed on healthy volunteers (human predictive patch tests, HPPTs) to identify chemicals that cause skin sensitization in humans. Test patches containing the substance are applied to an inconspicuous area of the skin, and after a certain period of time, the skin is examined for redness, swelling, or itching to diagnose a reaction.

However, human data from allergic contact dermatitis tests can often only be interpreted with considerable uncertainty. In many cases, the available data alone does not allow for a clear classification, especially if no sensitization was observed. The current GHS scheme for allergic contact dermatitis does not sufficiently take into account the effectiveness of skin-irritating chemicals.  The scheme is used to assess chemicals according to the Globally Harmonized System (GHS), which was developed by the United Nations (UN) for the classification and labeling of chemicals in order to create uniform criteria for hazard labeling worldwide.

NICEATM has developed an app to facilitate the work of subclassification.

A publication on this topic appeared in March 2024:
Herzler M, Abedini J, Allen DG, Germolec D, Gordon J, Ko HS, Matheson J, Reinke E, Strickland J, Thierse HJ, To K, Truax J, Vanselow JT, Kleinstreuer N. (2024). Use of human predictive patch test (HPPT) data for the classification of skin sensitization hazard and potency. Arch Toxicol. 2024 May;98(5):1253-1269. doi: 10.1007/s00204-023-03656-4. Epub 2024 Mar 14. PMID: 38483583; PMCID: PMC10965744.

Sources and further information:
https://ntp.niehs.nih.gov/whatwestudy/niceatm/test-method-evaluations/skin-sens/hppt/hppt-app

Additional information:
OECD Guideline No. 497, Defined Approaches on Skin Sensitisation:
https://www.oecd.org/en/publications/guideline-no-497-defined-approaches-on-skin-sensitisation_b92879a4-en.html