I occasionally put a semi permanent dye in for special occasions etc, so it could be four five or even six months between dyes. Should I be doing an allergy test each time? My sister had bad allergic reactions to hair dye do I'm cautious but would like to avoid faffing about each time !
I went back to a shade of hair dye I had previously used for years and years, after having a bit of a break to try other colours. I did the patch test in an uncharacteristic fit of responsibility and I reacted badly. V glad I did the test!