This is a single-center, double-blind, randomized study to compare the diagnostic performance (primary) and safety (secondary) of ascending doses of hydroxyisohexyl 3-cyclohexene carboxaldehyde (Lyral®) 0.40 - 0.20 - 0.10 mg/cm²and a control patch (ß-cyclodextrin and Povidone (PVP)), in 20 adult subjects who have a clinical history of contact dermatitis and have tested positive (current or previous patch test) to Lyral® or Fragrance Mix 2.