My mild allergy problem has been getting noticeably worse over the years. I have to take an anti-histamine tablet for longer in the year as time passes. Once, I was passing through Perth, Australia on a day when you could see a million miles and it was looking particularly hot and dry. I envioulsy said to the ground engineer how I would like to live in a climate like that with no hayfever. He soon put me right. There is a different spread of allergies living somewhere like that.
I read that absolutely no mention is made in any written records or stories anywhere from earlier than about 1900 of asthma or hayfever or allergies. I find this quite fascinating. They apparently didn't exist. In the 60s at my schools, usually about 1 person per class suffered such that they needed an inhaler. Now anything up to 20% of schoolchildren at any one time are under asthmatic therapy. Something extraordinary is happening in human allergy, and the effect is increasing violently.