Contact dermatitis is one of the most common types of occupational illnesses accounting for approximately 90–95% of all occupational skin disorders in the United States and resulting in a significant socioeconomic impact. Common symptoms of acute dermatitis include itching, pain, redness, swelling, and/or formation of a rash with the potential for chronic changes, including alteration in pigmentation, skin thickening, and cracking following repeated or prolonged exposure. Contact dermatitis can result from direct effects of the chemical on the skin, irritant contact dermatitis (ICD), or immune-mediated effects, including urticaria and ACD. The symptoms and presentation of ICD and ACD are similar, which often makes it difficult to distinguish between the two without clinical testing such as patch testing. The severity of contact dermatitis is highly variable and, similar to dermal absorption, depends on many factors including chemical properties of the hazardous agent, exposure concentration, duration and frequency of exposure, environmental factors, and condition of the skin. Chemicals responsible for direct or immune-mediated effects are capable of crossing the epidermal barrier and have certain physiochemical features such as lipophilicity, molecular size, and shape and reactivity that enable them to activate innate or adaptive immunity through the stimulation of secondary stimuli such as danger signals.18,19 ICD is a non-immunologic reaction that manifests as a local inflammation of the skin caused by direct damage to the skin following exposure to a hazardous agent. The reaction is typically localized to the site of contact. Available data indicate that ICD represents approximately 70–80% of all cases of occupational contact dermatitis.20