Basophils are a type of white blood cell that play an important role in the immune system. They work closely with your immune system to defend your body from allergens, pathogens, and parasites. Basophils release enzymes to improve blood flow and prevent blood clots. Basophils are one of three granulocytes, along with neutrophils and eosinophils. They are the smallest in number of granulocytes but the largest in cell size. Basophils play an important role in helping your body respond to allergic reactions.

A blood test can be performed to count the number of basophil cells in your blood. An increased number of basophil cells (basophilia) may be an indication of an underlying medical condition. Some conditions that reflect basophilia include hypothyroidism, myeloproliferative disorders, and autoimmune disorders. A low count of basophils (basopenia) can indicate other basophilic disorders such as cancer, acute infection, or a serious injury.

If your basophils are abnormal, there are no direct symptoms associated with your count itself. Any symptoms you experience are a sign of an underlying medical condition. Common symptoms of basophil conditions include itching, hives, and swelling. Your healthcare provider will examine your cells through a complete blood count test, where they will draw a sample of your blood from your vein to diagnose and screen for several diseases, conditions, and infections by measuring and counting your blood cells.