Interesting, Bob Morane, and welcome to the forum !
I too have challenge with histamine, but taking about 250mg vit C every morning helped me, in the long run, to reduce the histamine excess in my body ( vitamin C helps to boost histamine elimination). Quercetin also helps me a lot with histamine.
I agree that stress reduction is good too. I do not know what are positive neuroplasticity exercises, but I meditate every day, and it is good for many aspects of my health.
I cannot do DNA tests for SNPs for now, it would create problems with my business insurance, but when I will no longer own a business, I will most probably do a DNA test.
As a reply to Quantum
My DNA report shows Histamine related SNPs and I think it is directly related to POIS (at least for me)
"The DAO and HNMT genes both encode enzymes responsible for the breakdown of histamine within your body.
? You have genetic variants in the HNMT gene associated with reduced function, meaning that you may have
reduced ability to break histamines down effectively following exposure to environmental allergens."
I have noticed in the past how very similar my POIS symptoms are compared to histamine intolerance symptoms. It all makes sense to me since my POIS began specifically after a one month medical treatment with 3 different antibiotics at age 34. It severely damaged my microbiome and my ability to deal with histamine breakdown. Leaky gut, SIBO, dysbiosis... Immediately after this treatment I began reacting to high histamine foods and also I began suffering from POIS (although at that time in pre-internet 1986 I had no idea what was going on - it took me many years to figure it out). After ejaculation, I develop the same types of symptoms I get after ingestion of histamine rich foods, especially if a high level of stress is present (which also seems to contribute to increase histamine production). I have been periodically dealing with SIBO and other related conditions ever since. I am now 67 years old, so that was 33 years ago! Prior to this antibiotic exposure I had a very active sexual life without any issues at all. No POIS at all.
Needless to say I have been experimenting with stress reduction techniques, diet, probiotics and various supplements. I have had periods with very low level of POIS symptoms but as soon as I am in a difficult stressful situation or if I expand my diet to include more histamine rich foods (while traveling for example) or if my microbiome gets into a state of dysbiosis for various reasons, I need to redo all the work with a strict diet, positive neuroplasticity exercises (similar to meditation), and supplement with probiotics and more. This is where I am at currently.
The more we learn the better we can focus our actions and get results. Thanks for sharing your experience.
Hi Fox, and welcome to the forum !
I agree that many members had improvement when turning to a more healthy diet. Better nutrition is part of my own overall relief method. No more industrial food, no more MSG, no more aspartame, no more artificial flavor or color, no more refined sugar. And, for 4 years now, my green smoothies of organic veggies and fruits are an essential part of my diet. I have more energy now at 54 than I had at 35 
I think a healthier diet would help anybody, not just POIS sufferers, so it is a logical first step for any POIS sufferer.
Talking about healthy gut, did you tried some probiotics supplements with both strains of lactobacillus and strains of bifidus ? Flooding the guts with good bacteria really helps getting rid of the methane-producing ones. Clindamycine can help in theory to get rid of anaerobic bacteria, but after antibiotherapy is finished, the bacteria left will occupy the free space again, with time.
Channelopathies have been briefly discussed here. I do not exclude that it may be part of what causes my POIS, because taking potassium really helps with my fatigue, both for POIS and after physical exercise. As you mention in a previous post, it may be possible that a different set of unfavorable SNPs can be present in POIS sufferers, and depending on the specific set of SNPs one has, it determines the severity and exact symptoms list one shows when in POIS. This also would account for the fact that it seems to be more than just one type of POIS.
