I’ve heard anecdotal reports both ways with milk thistle seed and acne. I don’t think anyone knows how it works in regard to acne. In some cases when it helps then people like to attribute it to supporting the liver. In cases where it hurts then people also like to attribute it to supporting the liver, albeit “too quickly”. But in neither case is there much evidence to support the claims. Really, no one knows how milk thistle seed might be affecting acne.
Regarding allergies, I haven’t personally heard any reports of milk thistle seed allergies. But, as you indicate, there are cautions of allergic reactions possible in some conservative sites. But, at the same time, the studies demonstrate that milk thistle seed can be effective in resolving seasonal allergy symptoms.
All the studies that I know of show that milk thistle seed is anti-inflammatory. So it seems unlikely (though certainly not impossible) that milk thistle seed would cause inflammation. The seeds do contain small amounts of polyunsaturated fat and probably, due to being seeds, they are likely to contain some anti-nutrients. But since the amount used is so small, I cannot imagine that these things would cause any problems whatsoever except in extreme cases such as if one is otherwise starving.
With all that said, everyone responds to things differently. So it is possible that you are allergic to milk thistle seeds. Then again, it could be entirely coincidental that you are experiencing these symptoms. Or, it could be that, as some people suggest, the liver support may temporarily adjust conditions that would increase acne. Or, of course, it could be something else entirely.
Without knowing you, why you are taking milk thistle seed, what you eat or don’t eat, what other symptoms you have, lifestyle factors, etc., it is impossible to speculate too much. I do wonder what your motivation is for using milk thistle seed. If you are attempting to support liver health, then normally my first suggestions would be to eat enough food, going easy on polyunsaturated fat, eating sufficient carbohydrates, and ensuring that you are eating sufficient quality protein with an emphasis on glycine (as in gelatin). Also, if you tolerate them well then oranges (as in orange juice) and potatoes provide some nutrients that are good for liver health – particularly glucaric acid. All of which, of course, would be in the context of an *enjoyable* and *delicious* diet that is satisfying. Oh, and getting sufficient rest is super important.
The thing is that the liver is particularly good at regeneration. So as long as you eat enough and rest enough then it will be fine in most cases. Milk thistle seed is an excellent herb in most cases, but only if you are supporting liver health in basic ways.
You might want to just reduce the dose by half or even to 1/4 that, and see if that makes any difference. Or, just lay off entirely for a week or two and see if that changes anything.