What Causes Itchy Anal Area With Normal Stool Test?

I have had an itchy anus for several months now. At first I thought it was some sort of worm but I had a stool sample tested and it was negative. I feel it might be due to minor hemorrhoids because of food sensitivities and stress but there seems to be dry flaky skin around the anus now as well. It s very uncomfortable. I m very clean and hygienic. I don t use anything but castille soap if anything. I have allergies to fragrances and have undergone quite a bit of chemical allergy testing. It is worst at night but also bothers me during the day. Is there a natural cure or anti fungal that I can use? Should I look into surgery to remove the small hemorhoid? Thank you.