Although patch test is a golden standard for the diagnosis of allergic contact dermatitis,it has several drawbacks such as tedious operation,some subjectivity in interpretation,and the need of 2 to 3 visits for testees to complete the test.In vitro tests are more objective and safer than patch test.At present,in vitro tests mainly include lymphocyte transformation test,cytokine release assay,cell activation marker detection and other improved tests,which can be used to distinguish between allergic and non-allergic individuals by evaluating the function of lymphocytes.However,these methods,which have both advantages and disadvantages,are mainly in the exploratory stage and more researches are needed for their clinical application.