Allergy skin testing allows us to diagnose environmental, food, bee sting or medication allergies by observing if there are signs of a histamine release. Histamine, when released from the allergy cells in the skin known as mast cells, will cause a “wheal and flare” reaction. This reaction is a small hive, which is raised, red and itchy. Histamine causes this reaction by binding to histamine receptors in the skin.