ABSTRACT: Contact dermatitis of the nail unit is not rare. The most common allergens are found in nail cosmetics such as enamel, sculptured nails, and preformed plastic tips. Toluene sulfonamide formaldehyde resin, acrylates, and ethylcyanoacrylate are the most common allergens. Along with a proper clinical history focusing on nail practices, a thorough understanding of the common allergens and patch testing are necessary to diagnose contact dermatitis. A discussion of the common allergens and irritants relevant to the nail unit will be presented.