allergic reaction

so I stopped using pads when I was younger and changed to tampons because I would get a rash down there. and I would shower daily. it was really itchy and irritating and really uncomfortable. recently I have found that with tampons I will be itchy and uncomfortable on the inside when I stop menstruating and the last tampon is removed. I don't know if I'm allergic to something that is in tampons and pads. but it's really frustrating and itchy and irritating. please help me.