calimine lotion works well, not sure if I spelled it correct but it is in a pink bottle by the first aid stuff and should be only a couple of dollars. You could also use peroxide to dry it out and kill the bacteria. scratching it causes it to spread. I have had poison ivy many times as well as poison oak and I find that a combination of calimine lotion and peroxide used seperately (obviously don’t mix the two in a bowl lol) works best.
see below link: