Patch testing procedures are simple and painless. To identify specific triggers, your physician will tape several different patches that contain various potential irritants to the skin on the back. These chemicals are then left on the skin for up to 48 hours, and it is crucial that they dry during this time. It’s important to remember that there are a near-limitless number of patch tests that can be performed. Standard tests include 20 or more items. A negative test to one patch test does not necessarily mean that you do not have contact dermatitis. What this means is that you are not sensitized to any of the reagents tested. If all of the patches in the initial test are negative, additional tests may be recommended based on your history.