@mikki can answer for herself, but in my case, it’s dairy intolerance in general, but on a more specific level it’s known that dairy intolerance can exacerbate leaky gut issues and cause even more undigested food particles to leak through the intestinal lining resulting in issues above an beyond the basic dairy intolerance.
You might ask if leaky gut is an issue that’s contributing to headaches and it can exist even without HWC specifically, or dairy in general, why not go on a complete elimination diet and/or resolve leaky gut?
Because it’s hard!
Personally, if I can see a reduction in symptoms by eliminating something, such as HWC, that’s at least confirmation that it’s involved and something to be addressed. This does mean that I have to be careful to NOT replace HWC with yet another source of dairy for it to be a fair test.
I had NO HWC today and I didn’t have to take anything for headaches whereas in the days before this, I was popping aspirin and/or acetaminophen every time I could. That’s too soon to conclude that HWC is definitively causing the headaches, but it is suggestive.