The two most likely culprits here non-allergic histamine release. The term is slightly confusing, because the mechanism involves the activation of mast cells, which are part of the immune system. The distinction with 'non-allergic' is that the response isn't mediated by IgE, which is the defining characteristic of a bona-fine allergic response. This kind of response can occur anywhere from an hour to like 12 hours later, and usually affects the back, chest, and scalp more strongly than other areas.
Closely related to this is a sensitivity to sulfur-containing compounds. This can be simply a hypersensitivity to them, or actually a disruption of the sulfur metabolism of mast cells in the instance of non-allergic histamine release. Stuff like NAC and ALA do this to some people.
Interestingly for turbo nerds, it's a bit more common in things that assist liver health because a number of the relevant molecules contain reduced sulfur -- that's how they serve as anti-oxidants. The part of mast cell metabolism that's fucked up is the sulfur redox pathways.
If you want to keep using it, but don't to dose twice a day, you may be able to fix this with the cheapest second generation anti-histamine that you tolerate well, like cetirizine (Zyrtec) or loratadine (Claritin). Those don't make you (very) sleepy or cause dementia. Check against your other medications first, of course, and don't do this if your liver is actually fucked because they're hepatically metabolized.