I can't agree with you anymore. I always had a mild reaction to any types of oils that were put on my lips, which is the common thing to do for chapped lips. Some oils made it waaaay worse, with EC actually spreading past the vermillion border and even onto the skin outside of lips. My worst reactions came after application of tea tree oil, jojoba oil and coconut oil after 3-4 days of liberal use.
Thank you for writing this post, I have experienced this but for some reason, never thought about it beyond the point of "this doesn't work, move on to next oil/hydration of some sort".
And same as you, EC improves during summer, which has been reported by a large amount of EC sufferers here. The sun / Vit D / being a little more active / less depression / etc.
Please keep us updated on your treatment for this, I am very much looking forward to it and I will gladly share mine if I make any progress.
Thanks once again for writing about this, it opened a new and exciting window that I had never considered.