I only had nosebleed once in my life. When I was a teenager I was cycling so fast and far to a place, and then when I was standing up in that place I saw blood dripping on my shirt. I was panicking so much because I never had it before. I went to a bathroom and washed my nostrils repeatedly. After a few minutes thankfully the bleeding stopped. I had no idea what caused it. The air was not dry as it was a tropical place.