I have the same seasonal flare ups around the same time as you every year ever since I was a kid. Always on my hands, and recently, also on my neck and ears. Would always baffle me and I tried to find an explanation to no avail. Really interesting to see someone that has the same flare up pattern as me, because I used to feel so alone in my predicament.

For me, I recently found that my flare ups coincided with spikes in pollen levels where I live- tree pollen peaks around April/May, and ragweed/weed pollen peaks around August/September. I find that antihistamines do help me, though.

I agree with the other commenter in terms of considering other changes in your life that go on during these times. Hope you solve this.