I may be using the old name 5 Day Extended Patch Test. 4 or 5 years ago that was the name my doctor used and it did take 5 days. Just 2 months ago my same allergist ran more True Test panels which were not administered the first time and it was for 4 days. I wondered if that was because he was working a 4 day week, but with your information perhaps 4 days is the new normal. Another person mentioned a 3 day test, however on my 5 day test some allergens that showed up as mild on day 3 were rated high by day 5. Also some mild reactions didn't appear until day 5. Perhaps the recent tests have chemicals or natural elements that can be read sooner. Good questions other may know the answer to.