Which areas should be used for patch testing?

Under normal circumstances, patch tests should be applied to the normal skin on both sides of the spine on the back. The specific analysis is as follows:

Patch testing is a diagnostic procedure used to determine delayed-type contact hypersensitivity reactions in the body, primarily to detect sensitivity to certain chemicals. Patch tests are typically applied to the normal skin on both sides of the upper back near the spine, as the skin in these areas contains a higher number of dendritic cells, making it suitable for patch testing. If the back area is insufficient or cannot be used due to other reasons such as scars, acne, or extensive tattoos, alternative sites such as the outer side of the upper arm or thigh may be selected. The lower back and the flexor surfaces of the forearm are unsuitable for patch testing because their poor absorption capacity can lead to false-negative results.

During the patch testing period, vigorous activity should be avoided, scratching should be prevented, exposure to sunlight should be minimized, and sweating should be reduced. If the allergic reaction at the application site is severe, the patch should be promptly removed, the test should be discontinued, and medical treatment should be sought immediately.