BACKGROUND A high incidence of local itching subcutaneous nodules and aluminium allergy was observed in clinical trials of a new aluminium adsorbed pertussis vaccine in Gothenburg, Sweden, in the 1990s. A total of 495 children with itching nodules were patch tested with aluminium chloride hexahydrate 2% and an empty Finn Chamber®, 377 (76%) with positive reactions. When 241 of them were re-tested some years later 186 (3 out of 4) had unexpectedly lost their patch test reactivity. OBJECTIVE To investigate the long-term prognosis of vaccine-induced contact allergy to aluminium by a third patch test about 20 years after Patch test I. METHODS Twenty individuals with positive and 11 with negative results in Patch test II were tested a third time with the same sensitisers as in in the first two tests. Three additional aluminium preparations were also tested. RESULTS A total 15 out of 20 persons with positive results in the second test had lost their patch test reactivity. Two of 11 with negative tests had turned positive again. The addition of the preparations gave no conclusive results. CONCLUSIONS Contact allergy to aluminium caused by vaccination with aluminium-adsorbed vaccines in childhood seems to fade away with time as measured by loss of patch test reactivity.