Histamine is a hormone released by the immune system so if the levels are really high it causes inflammation affecting your blood vessels.
histamine acts on the H1 receptors found in the bronchioles, causing bronchoconstriction.
It doesn't atropine only acts on muscarinic receptors (it's a competitive antagonist here for ACh), but histamine acts on different receptors (histamine receptors). There is no direct interaction...
Eosinophils
Histamine causes the dilation of the small blood vessels while constrict the large blood vessels.