One of my early warning signs of an asthma flare is that my chin and neck will get itchy and I'll start scratching it.
It took a long time for me to learn this (a nurse pointed it out to me when I was doing it). I started tracking it and sure enough, it's one of my early warning signs of an asthma attack. Usually, there are other signs if I pay close attention (shallow breathing, fatigue, pale, etc).
Now it's in my asthma action plan that I use my rescue inhaler if I have my early warning signs. My husband also knows the signs and has – on many occasions – noticed the signs before I did.
I think we acclimate to asthma and sometimes don't notice when we're "getting bad" until it's too late and in we're in a full blown episode.
Here is a refresher on asthma symptoms, and a sample asthma action plan:
Have you noticed early warning signs for your asthma?