No other tea gave me headache before. I have a feeling that this could be flavored (artificially).
I sometimes wonder about this with some greener oolongs that have a floral scent, was it added to create an illusion of higher quality. I have one TKY right now that I strongly suspect.
There is a lot of Dong Ding out there that is not grown on DD, the name in some circles is simply synonymous with the style of oolong. Crazy. But the fact is, there is way more demand for DD than there is leaf. This is becoming more and more common with more and more teas. Darjeeling for instance.
I may be wrong, but the higher mountain oolongs tend to be more or less organic even though they are often NOT certified organic. However with some of the chaos going on right now, the best advice is to buy only from vendors you trust ... and even then ask questions.
I have enjoyed as many DDs as I have disliked, but it is very frustrating to say the least.
If a tea is giving you a headache and it is only that one selection, by all means, keep it for now but move on to another.