Basophils are a type of white blood cell that works 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.


A microscopic diagram of a basophil cell compared to other white blood cells, neutrophils and eosinophils.
Basophils are the largest white blood cell compared to the size of neutrophils and eosinophils.

What are basophils?

Basophils are a type of white blood cell. There are three types of white blood cells, each with its own function to boost your immune system, including granulocytes, monocytes and lymphocytes. 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 helping your body respond to allergic reactions.


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What do basophils do?

Basophils function to defend your body against:

Basophil cells are unique in that they don’t recognize pathogens they've already been exposed to. Instead, they attack any organism they see that is unfamiliar to your body. Basophils destroy foreign organisms by surrounding and ingesting them (phagocytosis).

What enzymes do basophils release?

During allergic reactions, basophils release two enzymes: histamine and heparin.

Histamine enlarges your blood vessels to improve blood flow and heal the affected area. Histamine opens pathways for other cells in your immune system to quickly target and respond to the allergen. You can identify when your basophil cells release histamines because you will experience physical symptoms of an allergic reaction like itchy skin, a runny nose and watery eyes.

Heparin is an enzyme that prevents blood from clotting too quickly.

The granules of basophils hold both histamine and heparin. When a foreign organism enters your body, your basophils activate and release these enzymes to assist your immune system’s response to destroy the organism.


Where are basophils located?

Basophils form in the soft tissue of your bones (bone marrow). After the cells mature, they travel through your bloodstream and migrate to damaged tissues to help heal the area after an injury.


What do basophils look like?

Basophils are microscopic cells that are spherical in shape. To view these cells under a microscope, a lab technician adds a stain or dye to the sample of cells, making the cells turn a shade of purple to black. The basophil cell has a two-lobed nucleus (which looks like two raindrops connected by a thin thread) that appears as black and tiny purple polka dot granules, which float in a light pink fluid (cytoplasm).

How many basophils are in my body?

Basophils are a type of white blood cell. White blood cells make up approximately 1% of all the cells in your body. Basophils are the smallest in quantity and make up less than 1% of all white blood cells.


Conditions and Disorders

What are the common conditions that affect basophils?

There are two types of conditions that affect your basophils based on how many basophils are in your body:

  • Basopenia, meaning that your body isn’t producing enough basophil cells.
  • Basophilia, meaning that you have too many basophil cells.

If you have basopenia, your basophil cells may be working to fight an infection or allergic reaction or your thyroid gland might be overactive (hyperthyroidism). Your healthcare provider will perform follow-up blood tests to diagnose and treat the underlying cause to bring your basophil count back to a normal level.

Having an increased number of basophil cells (basophilia) may be an indication of an underlying medical condition. Your healthcare provider will perform a blood test to count your cells, followed by additional tests to confirm the diagnosis. Conditions that reflect basophilia include:

Less severe reactions to an increased amount of basophils in your body include:

  • Allergic reaction.
  • Infection.
  • A side effect of a medication.

What are the common symptoms of basophil conditions?

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:

What are common tests to check the health of my basophil cells?

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.

Since basophils are a type of white blood cell, your healthcare provider will order a complete blood count with differential, which counts the five kinds of white blood cells in your blood sample to verify whether or not your cell count is too high, normal or too low.

Two tests that specifically identify the health of your basophils include:

  • Absolute basophil count: An absolute basophil count identifies how many basophils are present in a sample of your blood. The calculation for an absolute basophil count multiplies the percentage of basophils from a complete blood count by the total number of white blood cells from the same count. The results from this test identify whether or not your basophil count is too high, normal or too low.
  • Bone marrow biopsy: Your healthcare provider will insert a large needle into your bone marrow to extract a small sample. Then they will examine it to verify the quantity and quality of your cells based on where they form.

Often, your basophil count offers a suggestion to a condition, but additional tests are necessary to confirm the diagnosis.

What is a normal basophil count?

A normal basophil count is .5% to 1% of your white blood cell count. This equals about zero to 300 basophils per microliter of blood in healthy adults. If your basophil count is outside of those ranges, you would be at risk of acquiring a basophil-related condition.

What causes my basophil count to be too high?

Several factors could cause basophilia, including:

  • Your thyroid gland doesn’t produce enough thyroid hormones (hypothyroidism).
  • Your bone marrow produces too many cells and platelets (blood disorder).
  • A cell mutation targets your white blood cells (leukemia).

What causes my basophil count to be too low?

Basopenia could be the result of your basophils working overtime to attack an allergen or treat an infection that is taking longer than normal to heal. It could also be the result of your thyroid gland producing too much thyroid hormone.

What are common treatments for basophil conditions?

Common treatments for basophil conditions include:

  • Avoiding allergens or taking antihistamines.
  • Changing dosage or timing of medications under your healthcare provider’s direction.
  • Treating any underlying medical conditions.
  • Treating infections and injuries.


What are simple lifestyle tips to keep my basophils healthy?

You can keep your basophils healthy by:

  • Taking vitamins to boost your immune system (vitamin C, B6, E, zinc).
  • Avoiding allergens.
  • Eating a well-balanced diet.
  • Minimizing stress.

Additional Common Questions

What is the difference between mast cells and basophil cells?

Mast cells and basophil cells are both types of white blood cells that target allergic reactions. Mast cells are oblong shaped and basophil cells are spherical. Both cells contain a nucleus and granulocytes. The difference between mast cells and basophil cells is that mast cells contain about 90% more granulocytes than basophil cells (granulocytes appear as tiny polka dots within the cell). Mast cells also stay inside tissues throughout your body and basophil cells spend most of their lifespan traveling throughout your circulation system.

A note from Cleveland Clinic

When allergy season strikes, your runny nose and watery eyes indicate that your basophil cells are doing their job. Your healthcare provider will suggest an absolute basophil count to check for cell abnormalities, which could be the first step of a diagnosis of an underlying medical condition or offer treatment options for persistent allergies or infections.

Medically Reviewed

Last reviewed on 06/14/2022.

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