Do some reading into Histamine and this area. Some women even take the amino acid Histadine in order to boost levels. I know of 1 person personally who has had great results with it ...I only PERSONALLY know of one because most people are not as open talking about it, otherwise I feel I would know more.
I have read about this many times online and seen quite a bit of success with increasing histamine (low levels may be due to elevated copper -which breaks histamine down- a simple hair mineral test can confirm this- cost is usually around $75 US).
*I should add that histamine is required for cllmax (and released during it), and is not such a good idea IN MEN since too much can lead be one of the factors in Premature Ejaculation*