p-Phenylenediamine (PPD) - although its mainly used as a component of engineering polymers and composites like kevlar, it is also an ingredient in hair dyes which once sensitized to, becomes lifelong. One can develop active sensitization to products, including but not limited to black clothing, various inks, hair dye, dyed fur, dyed leather, and certain photographic products. Photographic developers, especially those containing metol
Quaternium-15 – preservative in cosmetic products (self-tanners, shampoo, nail polish, sunscreen) and in industrial products (polishes, paints and waxes). Sap from certain species of mangrove and agave
Soluble salts of platinum – see platinosis
Thiomersal – mercury compound used in local antiseptics and in vaccines
Topical anesthetics – such as pramoxine or diphenhydramine, after prolonged use
Topical steroid – see steroid allergy
Urushiol – oily coating from plants of Toxicodendron genus –  poison ivy, poison oak, and poison sumac. Also found in mango plants, mango skin, cashews, and smoke from burning urushiol-containing plants, which can cause skin as well as severe lung irritation. Mechanism
ACD arises as a result of two essential stages: an induction phase, which primes and sensitizes the immune system for an allergic response, and an elicitation phase, in which this response is triggered. As it involves a cell-mediated allergic response, ACD is termed a Type IV delayed hypersensitivity reaction, making it an exception in the usage of the designation "allergic," which otherwise usually refers to type I hypersensitivity reactions.
Functional biliary sphincter of Oddi disorder
If all of the above criteria are met, individuals are classified as having a functional biliary sphincter of Oddi disorder, if the testing of pancreatic enzymes (amylase and lipase) is normal.The old Milwaukee classification of biliary sphincter of Oddi dysfunction (SOD) used to divide the condition into three subtypes: but it is no longer in use. Type I included patients with biliary-type abdominal pain, with all of altered liver enzymes on blood testing, dilated biliary ducts on ultrasound or ERCP, and delayed bile clearance on HIDA scan. Type II included patients with biliary-type abdominal pain associated with at least one of the following: altered liver enzymes on blood testing, dilated biliary ducts on imaging tests, and delayed bile clearance on HIDA scan. Biliary-type pain in the absence of any sign of biliary or pancreatic alteration was the so-called Type III biliary SOD. The hypothesis that this pain could be linked to SOD has been studied in a large trial published in JAMA (2014)  where patients were randomized to sphincterotomy or sham surgery. Contrary to expectations, patients who were not subjected to sphincterotomy fared better. Overall, the investigators found that only 23% of the patients who underwent sphincterotomy  improved versus 37% of the control group. The EPISOD trial has substantiated the ineffectiveness of endoscopic sphincterotomy in patients with these symptoms and SOD Type III is no longer considered to be a clinical entity.