Blisters may form and break, leaving crusts and scales. Later the skin may darken and become leathery and cracked. Allergic contact dermatitis can be difficult to tell from other rashes. The dermatologist and patient will discuss the materials that touch the person's skin at work and home, to identify the allergen. The dermatologist may also perform patch tests.
Patch tests are a safe and easy way to diagnose contact allergies.
Small amounts of the possible allergens are applied to the skin for a fixed time, usually two days. Common allergens include nickel, rubber, dyes, preservatives, fragrances, and poison ivy, poison oak, and related plants. Nickel Dermatitis Nickel, part of certain metals, is found in many products. Many chrome-plated objects contain enough nickel to produce a reaction in sensitive people. Stainless steel also contains nickel, but it is bound so tightly that it is safe for most nickel-sensitive individuals.