Basophils are white blood cells from the bone marrow that play a role in keeping the immune system functioning correctly.

Doctors may order basophil level tests to help diagnose certain health problems. If basophil levels are low, this may be a sign of an allergic reaction or another condition. High basophil levels may indicate an autoimmune condition or one of several types of blood disorders.

What are basophils?

The body makes different types of white blood cells, which are vital components of the immune system.
White blood cells help keep the body healthy by fighting off invading germs, such as bacteria, viruses, and fungi.
Basophils are a type of white blood cell called a granulocyte. There are other forms of granulocyte, such as neutrophils and eosinophils.
Granulocyte cells contain granules, which they use to secrete important substances.
The granules inside basophils contain heparin, histamine, and other molecules that play a role in inflammation.

Function

Basophils are necessary for the immune system’s natural response to invaders, such as infectious germs.
The body’s response to allergens also involves basophils. When a potentially harmful allergen enters the body, the immune system responds by trying to isolate and eliminate the allergen.
When responding to an allergen, basophils that sustain damage will release histamine, which is partially responsible for inflammation during an allergic reaction.
Additionally, basophils play an integral role in preventing blood clotting. The heparin inside the cells is a form of natural blood thinner that helps keep the blood flowing through the body.

Tests

Doctors believe that the role of basophils in the body is reactionary, meaning that their number will generally only rise or fall due to an invader or underlying chronic issue.
This characteristic allows doctors to use basophil tests to help them identify underlying conditions and severe allergic reactions.
Doctors can use a complete blood count (CBC) to check a person’s basophil levels. A basophil count that is higher or lower than the normal range may prompt them to order additional tests.
A white blood cell count (WBC) test may be necessary to find the absolute basophil count in some cases. This test can help doctors get a better picture of the range of basophils in the blood.
Doctors may also order a specific test called a basophil activation test (BAT) to check for particular allergens.
During the BAT, medical professionals in a laboratory apply potential allergens to a sample of the person’s blood. If the person has an allergy, the basophils in their blood sample will activate specific molecules.
A 2016 study trusted Source found that the BAT is highly accurate in confirming food allergies. It may also be helpful for monitoring the immune system’s response to food allergens.
The BAT is a low-risk test compared with the oral food challenge test, which has the potential to trigger a dangerous allergic reaction.

Normal range

Although they have an essential function in the immune system, basophils only make up a small percentage of the total number of white blood cells. In a normal test result, they may contribute to less than 0.5 percent of the total white blood cell count.