Blood film facts for kids

A blood film (also called a blood smear) is a special way doctors look at your blood. It's a very thin layer of blood spread out on a glass slide. This slide is then stained with special colors. These colors help doctors see the different parts of your blood, like red blood cells, white blood cells, and platelets, under a powerful microscope. Doctors often use blood films to find out about problems with blood. Sometimes, they also use them to check for tiny living things (parasites) that can live in the blood, like those that cause malaria.

Blood films, stained with a special dye called Giemsa.

What is a Blood Film?

A blood film is like a tiny window into your blood. To make one, a small drop of blood is taken, usually from a finger or arm. This drop is then carefully spread very thinly onto a clean glass slide. It looks a bit like spreading butter on toast, but much thinner! After the blood dries, special dyes are added. These dyes make the different parts of the blood stand out with different colors. This way, doctors can easily see them when they look through a microscope.

Why Do Doctors Use Blood Films?

Doctors use blood films for many important reasons. They help doctors understand what's happening inside your body. For example, if someone is feeling very tired, a blood film can show if they have too few red blood cells, which is a condition called anemia. It can also help find out if someone has an infection by looking at their white blood cells.

How is a Blood Film Made?

Making a blood film is a simple process:

• Step 1: Getting the blood. A healthcare worker will gently prick a finger or take a small amount of blood from a vein in your arm.
• Step 2: Spreading the blood. A tiny drop of this blood is placed on one end of a clean glass slide. Another slide is then used to quickly spread the drop into a very thin, even layer across the first slide. This thin layer is the "film."
• Step 3: Drying and staining. The blood film is left to air dry. Then, special chemical dyes are added. These dyes stick to different parts of the blood cells, making them different colors. This makes it much easier to see them clearly under a microscope.
• Step 4: Looking under the microscope. A trained doctor or scientist then examines the stained blood film using a powerful microscope. They look at the size, shape, and number of each type of blood cell.

What Do Doctors Look For?

When doctors look at a blood film, they are checking for several things:

• Red Blood Cells: These cells carry oxygen around your body. Doctors check their shape, size, and how many there are. Problems with red blood cells can point to conditions like anemia or sickle cell disease.
• White Blood Cells: These cells are part of your body's defense system, fighting off infections. Doctors count the different types of white blood cells and check if they look healthy. Unusual numbers or shapes can suggest infections, allergies, or other serious conditions.
• Platelets: These tiny pieces help your blood clot when you get a cut. Doctors check their number and how they look. Too few platelets can mean you might bleed easily, while too many can cause problems with blood clots.
• Parasites: Sometimes, tiny living things called parasites can live inside blood cells. For example, the parasite that causes malaria can be seen inside red blood cells on a blood film. This helps doctors diagnose and treat these infections.

Blood films are a very important tool that helps doctors understand your health and find out what might be making you sick.

Images for kids

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  Variations of red blood cell shape on blood film, overall termed poikilocytosis

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  Blood smears showing various developmental stages of the malaria parasite Plasmodium falciparum, stained with Wright stain and Giemsa stain

See also

In Spanish: Frotis de sangre para niños