Kinda depends I think. We spent the last three months of last year, and the first three of this at sea level, right on the water in WA state. Then moved to 6500 ft in Wyoming. Really dry air there. Within a week I got the nosebleed from hell. We are not talking a drip here, but a flow. Went to the local urgent care, where the dr worked on me for over two hours, and could not get it to stop. So then we drove 75 miles to a hospital, where they had to use cocaine to get it to stop. Thankfully I didn't have to take a drug test the next day. Dr said to put some neosporin type stuff in my nostrils, and get a humidifier. Did both, no more bleeds. We assume that going up in altitude, and to a much dryer air, was the cause, the humidifier was worth the money...