about Seborrheic Dermatitis been said that some lack of b vitamins like b2 b6 biotin, can cause that.
b2 mentioned in related to chilitis.
homocystein test can show you if you deficient in b vitamins.
MTHFR gene Mutations can cause your body not to be able using b vitamins properly. tests my show you are not deficient in b vitamins, but it is not correct if you have mthfr mutation and then your body can't make use of the b vitamins which means you deficent in them.
the soulution from what i read is taking coanzymed forms of the b vitamins.