Owing to the widespread use of isocyanate-derived products across multiple industries, it is important for physicians to be aware of their sensitizing potential. We first provide a general overview of isocyanates and the industries that may be associated with exposure to these compounds. This is followed by a description of the most commonly used isocyanate products in commercial patch test preparations. Finally, we discuss appropriate isocyanate patch testing methodology and optimal isocyanate patch test concentrations.