Basophilia: symptoms and causes too high a number of basophils

Basophilia refers to an increase in the number of basophils, a certain type of white blood cells, in the blood. Basophils or basophilic granulocytes are produced in the bone marrow and are part of the cellular immune system. This includes white blood cells, leukocytes, which are differentiated according to their function. There are granulocytes, lymphocytes and monocytes. Granulocytes are divided into basophilic, eosinophilic and neutrophilic granulocytes. These subgroups take on different tasks in the immune system. Basophil granulocytes, for example, are involved in the defense against parasites. But they can also cause inflammatory and allergic reactions. Inside they carry messenger substances that (when released) can cause or intensify an allergic reaction. When the basophilic granulocytes migrate into the skin and release the messenger substance histamine, they cause severe itching.

  • What is basophilia?
  • What types of granulocytes are there?
  • What are granulocytes?
  • Species
  • Role and function of the basophil granulocytes
  • Immune defense
  • Messenger fabrics
  • Allergies and inflammatory reactions
  • Normal values
  • Symptoms of too high a basophil count
  • Causes: increased number of basophil granulocytes
  • Therapy


What is basophilia?

An increase in the number of basophilic granulocytes (so-called ‘basophils’, a certain type of white blood cells) in the blood is called basophilia. It is usually accompanied by an increased production of eosinophils, which increases the two blood values ‘basophils ‘ and ‘eosinophils’. Basophils belong to the group of granulocytes. Like eosinophils, they play an important role in defending against parasites and controlling allergic reactions. The granulocytes can be divided into neutrophilic, basophilic and eosinophilic granulocytes, of which the basophils are the least common. Their share in the leukocytes is usually only about up to a maximum of 2 percent. The percentage of basophilic granulocytes in the blood is therefore low, but in certain diseases their number increases.

What types of granulocytes are there?

What are granulocytes?

Granulocytes are a subgroup of white blood cells (leukocytes). Leukocytes are blood cells that recognize and eliminate invading pathogens and foreign bodies. They are part of the immune system. The leukocytes are divided into three subgroups, they differ in structure, shape and function:

  • granulocytes
  • lymphocytes
  • monocytes



Granulocytes form the largest group of white blood cells (leukocytes) with approximately 50 to 70 percent. They are formed in the bone marrow, from there they are released into the blood, where they circulate until an event occurs that requires them. Invading pathogens, cells of the immune system or damaged tissue send substances (messengers, so-called chemokines) that attract granulocytes. These migrate specifically to the affected tissue (chemotaxis) and fight the invaders through various mechanisms. The granulocytes are divided into three groups:

  • neutrophil granulocytes
  • eosinophilic granulocytes
  • basophilic granulocytes

Basophils release substances that cause inflammation and attract other cells for immune defense. Neutrophils recognize , destroy and eliminate pathogens or cell material as so-called phagocytes. Phagocytes clear away harmful foreign particles, bacteria, and dead or dying cells. Eosinophils are mainly concerned with the defense against parasites by releasing harmful substances, they participate in the development of allergies and sometimes they are active as phagocytes.

Role and function of the basophil granulocytes

Immune defense

Basophilic granulocytes make up the smallest proportion of granulocytes (up to roughly two percent). They are spherical and 10 to 16 μm (micrometers) in diameter, slightly smaller than eosinophils and neutrophils. The granules in the cell look dark purple to blue under the microscope. Like all leukocytes, they are formed in the bone marrow and live only a few days. They are named after the basophilic ingredients of the granules, for example histamine and heparin. Basophils have various tasks and are involved in immune defense, such as:

  • detection and destruction of degenerated cells in the early stages of cancer
  • participation in defense against parasites and fungi
  • wound healing


Messenger fabrics

One function of the basophil granulocytes is to release messenger substances when they encounter invaders. The messenger substances are regarded as a chemical signal that particularly attracts eosinophils. These fight the intruder or foreign body. As a result, the basophils are indirectly involved in the fight against pathogens, especially parasites.

Allergies and inflammatory reactions

It also plays a role in allergies and inflammatory reactions. The surface of basophilic granulocytes has receptors for certain exogenous substances, so-called antigens. Once antigens such as pollen attach to the correct receptor on the basophil granulocytes, substances stored in the granules, such as heparin or histamine, are released. The release of histamine leads to an immediate allergic reaction: type I allergy. Vascular dilation occurs and thus increased vascular permeability. The production of mucus is increased, with simultaneous contraction of the respiratory muscles. The airways are narrowed. Depending on the severity of the allergic reactions, this leads to the classic symptoms of an allergy:

  • reddening of the skin
  • itch
  • drop in blood pressure
  • difficult breathing


Normal values

The normal value for basophils in adults is approximately 15 to 50 per microliter (µl) of blood. The value fluctuates during the day, making the range of normal values relatively large. However, the number of blood cells is usually not given as a number, but as a ratio to the total number of leukocytes: the normal value is between 0 and a maximum of 2 percent.

Symptoms of too high a basophil count

Large numbers of basophils can cause itching and other symptoms and signs of an allergic reaction. Allergies and allergic reactions to foods and medications are a common cause of basophilia. Any other symptoms depend on the condition causing the problem.

Causes: increased number of basophil granulocytes

Basophils or basophilic granulocytes are increased in the following diseases:

  • certain types of blood cancer, such as chronic myelogenous leukemia
  • polycythemia, a blood disorder characterized by an abnormal increase in the number of red blood cells in the blood
  • chronic inflammatory diseases such as rheumatoid arthritis (RA)
  • parasitic infection
  • Ulcerative colitis, a chronic inflammation of the lining of the large intestine
  • underactive thyroid gland (hypothyroidism)
  • diseases with elevated blood lipid levels such as diabetes mellitus, kidney diseases



An excessively high basophil count is often discovered incidentally in a blood test when a blood count (the number of red blood cells, white blood cells and platelets in a blood sample) is performed for other reasons. The doctor will look at the values with the rest of the blood count and, if necessary, conduct further tests to diagnose possible diseases. The treatment is aimed at the underlying cause.

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