Basophils are a type of white blood cell in your immune system that help defend your body from allergens, pathogens and parasites. Basophils release histamine to improve blood flow to damaged tissue and heparin to prevent unwanted blood clots. Abnormal basophil levels may indicate various conditions, from allergic reactions to cancer.

Overview

Basophils are the largest white blood cell compared to the size of neutrophils and eosinophils.

What are basophils?

Basophils are white blood cells in your immune system that protect your body from infections and allergens. They’re also one of three types of granulocytes. Compared to the other two types of granulocytes in your blood — neutrophils and eosinophils — basophils are the fewest in number but the largest in size.

Basophils play an especially important role in helping your body fight allergens. Symptoms like itchy skin, a runny nose and watery eyes are signs that basophils are working to get rid of a foreign substance in your body.

Function

What do basophils do?

Basophils have several functions. They:

  • Defend your body against invaders. They help fight parasites, bacteria, viruses and fungi.
  • Trigger allergic reactions allergens and infections. They release histamine, which triggers symptoms of an allergic reaction.
  • Prevent blood clots that may slow healing. They release heparin to prevent blood from clotting in an area where an invading organism or allergen has caused damage. Blood needs to reach the area so it can heal.

Basophils are different from some other types of white blood cells in that they don’t recognize foreign organisms (pathogens) they've already been exposed to. Instead, they attack any organism they find that’s unfamiliar to your body. Basophils destroy these invaders by surrounding and ingesting them (phagocytosis).

Anatomy

Where are basophils located?

Basophils form in the soft tissue inside your bones (bone marrow). After they mature, they travel through your bloodstream until they reach damaged tissues. They help heal the area.

What do basophils look like?

Basophils are microscopic cells that are spherical in shape. They have a two-lobed nucleus (which looks like two raindrops connected by a thin thread). To view these cells under a microscope, a lab technician adds a stain or dye to the sample of cells. This makes the cells turn a shade of purple to black. It causes the granules inside to appear as tiny purple polka dots.

How many basophils are in my body?

Basophils make up less than 1% of all of your white blood cells, making them the least common type. In a blood test, a normal basophil count is .5% to 1% of your total white blood cells. This equals about 0 to 300 basophils per microliter of blood in healthy adults.

A basophil count outside of this range means you may have a basophil-related condition.

Conditions and Disorders

What are the common conditions that affect basophils?

Two types of conditions affect your basophils:

In both cases, your healthcare provider may need to run tests to determine what’s causing your basophil counts to be outside the normal range.

Common symptoms of basophil-related conditions

There aren’t any direct symptoms associated with an abnormal basophil count. Any symptoms you experience are a sign of an underlying medical condition.

Symptoms of conditions that affect your basophils include:

Common tests to check the health of basophils

As basophils are a type of white blood cell, your healthcare provider will order a complete blood count (CBC) with differential. This test counts all the types of white blood cells in a blood sample to check whether your white blood cell count is too high, normal or too low.

An absolute basophil count (ABC) identifies how many basophils specifically are present in a blood sample. The calculation multiplies the percentage of basophils from a CBC by the total number of white blood cells in the same count.

Abnormal basophil levels may indicate a condition, but your healthcare provider will need to do more tests to confirm a diagnosis.

Common treatments for basophil-related conditions

Treatments for conditions that affect your basophils include:

  • Taking antihistamines.
  • Taking medications to fight an infection or calm inflammation.
  • Changing the dosage or timing of medications (under your healthcare provider’s direction).
  • Treating any underlying medical conditions.

Care

What are simple lifestyle tips to keep my basophils healthy?

You can keep your basophils healthy by:

Additional Common Questions

Is it better to have high or low basophils?

It’s not better to have high basophils rather than low basophils — or vice versa. Both may be a sign of a long-term condition that requires ongoing treatment. Or the abnormal levels may be a sign of something that is easier to address, like a medication side effect. Your healthcare provider will do more investigating to be sure.

A note from Wockr

When allergy season strikes, your runny nose and watery eyes indicate that your basophils are doing their job. Your healthcare provider will suggest an absolute basophil count (ABC) to check for cell abnormalities. This may be the first step your provider takes toward diagnosing an underlying medical condition or recommending treatment options for persistent allergies or infections.