Does clinical testing support the current guidance definition of prolonged contact for nickel allergy?

The majority of nickel-allergic subjects did not react to nickel discs after 2 hours or after repetitive exposures of up to 30 minutes on 3 occasions over a period of 2 weeks. The length of time needed to cause nickel allergic contact dermatitis in most nickel-allergic individuals is longer than the ECHA guidance definition. Longer test times are needed to define the time required to cause dermatitis in most nickel-allergic individuals. As a limitation, the test conditions did not adequately assess real-life factors such as friction, which is relevant for some uses of nickel.