Basophils are a type of white blood cell that have some role in immune surveillance (such as detecting and destroying very early cancers) and wound repair. Basophils can release histamine and other mediators and play a role in the initiation of allergic reactions.
Basophils account for less than 3% of the circulating white blood cells (0 to 300 basophils per microliter of blood).
An increase in the number of basophils (basophilia) can occur in people with hypothyroidism. In the myeloproliferative disorders (for example, polycythemia vera and myelofibrosis), a marked increase in the number of basophils can occur.
The symptoms usually depend on the disorder that is causing the change in the number of basophils, but increased numbers of basophils can cause itching and other allergic reactions.
The change in the number of basophils is usually detected by chance when a complete blood count is done for other reasons.
Treatment is directed at the disorder that is causing the change in the number of basophils.