Methyl donors, mold/CIRS, histamine reaction

Does anyone understand why some of us who are dealing with mold illness/CIRS react so badly to methyl donors like b12? Is it just that they increase histamine when we already have too much histamine in our systems wreaking havoc? I do have a1298c so I think that compromises methylation some. I am one year in on mold/cirs treatment w a doc at Cleveland Clinic Functional Med and I am making progress. Histamine intolerance is considerably better as I take glutathione, binders and infrared sauna as I work to reduce mold in my system. Can anyone explain what's going on in my body to make make me so unwell from things like B12 or folate as I try to reduce homocysteine? I know mold seriously affects methylation, immune system, histamine and inflammation. I don't understand details it is so complicated! My doctor just says as we get the mold out of my system, histamine will come down and I will be able to tolerate. I know on page 31 of Dr Neil Nathan's toxic book he actually talks about mold illness and b12 intolerance. My homocysteine is high (18) so we are trying folinic acid and even though I feel my hypersensitive system has settled down a good bit, I still cannot take folate or b12 of any kind! When I do, the next day I wake up and feel like I've been hit by a truck with body aches and no energy and puffy eyes way worse then my normal bad. I would love to understand why this is happening and how does one reduce homocysteine if they're intolerant to these methyl donors?