Yes, magnesium has helped.
For me, avoiding high histamine foods as well as histamine liberators had helped tremendously.
The theory:
Anti-histamines like Benadryl make you sleepy by blocking histamine.
Well, instead of blocking the histamine, get rid of it in the first place by avoiding histamine foods (for example aged or preserved meats).
Histamine has different pools, functions, and receptors in the body. You’re reducing it all to one single level that goes up or down with diet but that’s not how it works.
The brain histamine in your neurons is primarily synthesized from an amino acid. The histamine levels in neurons are different than the levels in mast cells.
There are a lot of degrees of hand waving in your theory that don’t work.