What does high Baso in blood mean?

Basophils. Are a certain type of white blood cell. They contain histamine and can become elevated in inflammatory and allergic conditions.
Usually less then 1% A basophil is a white cell in the granulocyte family that is characterized by a pale nucleus and large densely basophilic granules. It usually represents 0.5 to 1% of circulating white cells. It can be high in certain leukemias, advanced anemia, malaria and plumbism and other problems.