Cause of vasodilation in spider nevi
B i.e. EstrogenIn chronic liver disease (especially cirrhosis) and pregnancy, impaired estrogen metabolism and consequent hyper estroenemiaQ leads to spider angiomata/nevi (superficial, toous aerioles, that unlike simple telangiectases, typically fill from the center outwards and occur invariably on upper half of body) and palmar erythema (mottled redness of thenar & hypothenar eminences).
Testosterone
Estrogen
FSH
Hepatotoxin