Limonene is found in cosmetics, fine fragrances and hygiene products as well as in household and industrial products. Limonene is one of the most commonly found fragrance ingredients in consumer products presently available. Limonene is a naturally occurring terpene, present in large amounts in various citrus fruits. Limonene autoxidize on air exposure at room temperature forming hydroperoxides. Compared to pure unoxidized limonene the hydroperoxides of oxidized limonene have shown to be far more allergenic. NOTE: The preparation contains 3% oxidized limonene. The concentration of the active haptens in the preparation is measured from the added amount of the hydroperoxides of d-limonene.The Hydroperxides of Limonene is also available for testing in a lower concentration (H-032B). Using this lower concentration will decrease the risk of obtaining false positive test results.