Basophils are a type of white blood cell. Although they’re produced in the bone marrow, they’re found in many tissues throughout your body. Their normal blood range should be under 300 per microliter.

Your body naturally produces several different types of white blood cells. White blood cells work to keep you healthy by fighting off viruses, bacteria, parasites, and fungi. Basophils are part of your immune system and play a role in its proper function.

If your basophil level is low, it may be due to a severe allergic reaction. If you develop an infection, it may take longer to heal. In some cases, having too many basophils can be caused by certain blood cancers.

Your doctor can determine whether your white blood cell count falls within an acceptable range. Your doctor may recommend that you get your blood work completed at every annual checkup.

Whether you scrape yourself during a fall or develop an infection from a wound, you can count on your basophils help to get you healthy again.

In addition to fighting parasitic infections, basophils play a role in:

Preventing blood clotting: Basophils contain heparin. This is a naturally occurring blood-thinning substance.

Mediating allergic reactions: In allergic reactions, the immune system is exposed to an allergen. Basophils release histamine during allergic reactions. Basophils are also thought to play a role in causing the body to produce the antibody called immunoglobulin E (IgE).

This antibody then binds to basophils and a similar type of cell called mast cells. These cells release substances such as histamines and serotonin. They mediate the inflammatory response in the area of your body that was exposed to the allergen.

Basophils account for less than three percent of your white blood cells. You should have 0 to 300 basophils per microliter of blood. Remember that blood test normal ranges can vary from lab to lab.

Blood testing is the only way to discover whether your basophils are abnormal. There typically aren’t any exact symptoms tied to an abnormal level, and doctors rarely order a test just for a basophil count.

Blood tests are usually performed during a general wellness check or when investigating some other issue.

Learn more: White blood cell count and differential »

The following can cause your basophil level to be high:

Hypothyroidism: This occurs when your thyroid gland doesn’t produce enough thyroid hormone. If your thyroid hormone is low, it can cause your bodily functions to slow down.

Symptoms include:

  • puffy face
  • hoarse voice
  • brittle hair
  • coarse skin
  • weight gain
  • constipation
  • inability to feel comfortable when the temperature drops

Myeloproliferative disorders: This refers to a group of conditions that cause too many white blood cells, red blood cells, or platelets be to produced in your bone marrow.

Although a rarity, these disorders can progress into leukemia. Leukemia is a cancer of white blood cells.

Major types of myeloproliferative disorders include:

  • Polycythemia rubra vera: This blood disorder results in an overproduction of red blood cells. Symptoms include feeling tired, weak, and short of breath.
  • Myelofibrosis: This disorder occurs when fibrous tissues replace blood-producing cells in the bone marrow. It can cause anemia, an enlarged spleen, and oddly shaped red blood cells. Symptoms include feeling tired, an abnormal amount of bleeding or bleeding too easily, fever, and bone pain.
  • Thrombocythemia: This disorder causes an overproduction of platelets, leading to blood clotting or less commonly, extra bleeding. Symptoms include a burning sensation, redness, and tingling on your hands and feet. You may also have cold fingertips.

Autoimmune inflammation: This occurs when your immune system attacks your own body.

Symptoms include:

  • inflamed joints
  • fever
  • hair loss
  • muscle pain

The following can cause your basophil level to be low:

Hyperthyroidism: This happens when your thyroid gland produces too much thyroid hormone. The excess hormone causes your bodily functions to speed up.

Symptoms include an:

  • increased heart rate
  • increased blood pressure
  • excessive sweating
  • weight loss

Infections: This occurs when bacteria or other harmful substances enter an injured part of the body. Symptoms run the gamut from pus and pain when touched to fever and diarrhea.

Acute hypersensitivity reactions: In this case, your body overreacts to a substance in the form of an acute allergic reaction.

Symptoms include:

  • watery eyes
  • runny nose
  • red rash and itchy hives

In extreme situations, symptoms can become life-threatening. If you have an anaphylactic reaction and are unable to breathe, emergency medical attention is necessary.

Learn more: Anaphylaxis »

Your body contains multiple types of white blood cells, and all help protect you from diseases.

Basophils are granulocytes. This group of white blood cell contains granules full of enzymes. These enzymes are released if an infection is detected and if an allergic reaction or asthma attack takes place. They originate and mature in the bone marrow.

Other types of granulocytes include:

Neutrophils: This is the largest group of white blood cells in your body. They help fight infections.

Eosinophils: These help cells combat parasite infections. Like basophils and mast cells, they play a role in allergic reactions, asthma, and fighting parasite pathogens. They also develop in the bone marrow before moving into your blood.

The other main types of white blood cells are:

Lymphocytes: These cells are part of your immune system. They attack pathogens, including bacteria and viruses.

Monocytes: These cells are part of your immune system. They fight infections, help remove damaged tissues, and destroy cancer cells.