Just parking this one here as a "think aloud." My thought processes is: Vascular insufficiency = vascular permeability. Elevated histamines = vascular permeability. Mold (or toxins, or allergens, and/or gut imbalances) = increased histamine levels.
Source: Research Gate
AND, why I'm thinking about this:
Itching for Answers, How Histamine Relaxes Lymphatic Vessels
"Histamine is usually thought of as a component of mast cell degranulation that mediates vascular responses to inflammatory stimuli. The effects of histamine on the lymphatic vasculature have been confounded by inconsistencies between various experiments performed in the past, thus a definitive role has been elusive. The two studies discussed in this editorial show that not only does histamine inhibit lymphatic contractions that are important for pumping lymph and antigen to downstream lymph nodes, but that it can also be released by lymphatic endothelial cells to do so."