POIS is a tricky illness and one with multiple symptoms that can be different from on POISer to another. One theory suggests a huge similarity between Mast Cell Activation Syndrome ( MCAS ) and POIS. Another theory supposes an auto-immune reaction to seminal fluid as proposed by Waldinger
(1). Though it is much more likely that POIS can be a case of Mast Cell Activation Disorder ( MCAD ) through auto-immune signaling of IgG anti-bodies.
(2)A huge part of the debilitating effects of POIS symptoms are those that are related to Central Nervous System ( CNS ). One of them are the Cognitive cascade of symptoms that involve debilitating Cognitive an Social problems. These problems are supposed to be caused by the inflammation that occurs in the CNS. Typically suggested treatments for such problem are anti-histamines or NSAID. The later treatment is inconsistent and personally never worked for me. The former is also inconstant and it also never worked for me. In both cases it might have worked for some people but not for me, nor for others. This is strikingly similar to the case of MCAS.
Thus I suggest an investigation of the role of Histamine H3 receptors which are primarily located in the CNS; Which are, unlike the H1 receptor, possess an anti-inflammatory effect
(3). Yet, they also possess an inhibitory role of many neurotransmitters such as ( Dopamine, GABA, acetylecholine, neuradrenaline, histamine, serotonin, etc.)
(4). It could be that H3 histamine is released during neuroinflammation to counter act the release of histamine H1 which can cause damage to these neurons, but by its release it inhibits the function of many neurotransmitters and thus it inhibits many functions in the brain.
A way to investigate this theory is to try Histamine H3 receptor antagonists. Such as Betahistine, or Ciproxifan and Wakix (if available to you) under professional medical supervision. I don't have access to these drugs personally but maybe it'll help folks who do have access to it.
Best of luck to you all.