I, too, have been getting headaches an hour or so after I ride. Personally, I think it's because of the spring - the roads are still dirty and have the salt (or whatever it really is) on them, I'm breathing it in through my nose and into my sinuses- not to mention the dampness in the air. I've chalked it up to that. What has been helping a lot is that I use a saline nasal spray right after I come in from the ride. It has made a difference and I recommend it. It couldn't hurt - and it might help. I don't get headaches like this in the winter or in the summer after, say, May. Those are my .02 .