Biocompatibility testing occurs in the forms of cytotoxicity, irritation, hemocompatibility, sensitization, carcinogenicity, or any other biological effect listed on the ISO-10993-1 toxicity test matrix. For obvious reasons, the quantity of testing done is proportional to the extent and duration to which the medical device interfaces with the patient. Surface devices/treatments that are placed on the skin (such as anti-dryness lotion from Loreal) mainly undergo testing in ADME, cytotoxicity, sensitivity, and irritation since it does not permeate throughout the body. This type of testing used to be done on animal models, but has transitioned to being tested on human skin that has been tissue-engineered from skin-cells in order to attain more accurate results while circumventing the euthanasia of animals. Biocompatibility testing for a more invasive device, such as a cardiac stent involves in vitro and in vivo testing involving systemic toxicity, chronic toxicity testing depending on how long the stent is intended to stay in the patient, as well as implantation, hemocompatibility, carcinogenicity, and genotoxicity. This extensive testing is done to account for any unwanted byproducts released into the blood, which can travel to other parts of the body and result in complications for the patient that were not initially present.