Hairdye???

I usually have my hair coloured at my hairdressers but this time i want to do it myself. The other day i brought a loreal one and did the tester behind my ear and it stung and went really red. It has now left a small scab behind my ear so i didn't use it because of the reaction. Today i brought 'Garnier nutrisse cream' and i did the tester behind my ear (like instructed) this morning. At first it was a tiny bit itchy and it my skin went slightly pink, but it soon went off, so i kept reapplying the tester. It says i have to leave it on for 48 hours before i actually use it. It isn't pink and doesn't itch now but i was just wondering is it safe for me to use? Also how am i supposed to wash my hair? Because it says not to wash the tester off.