Although psoriasis mostly shows up on the skin, it can also reach other parts of the body. If you’ve ever looked at your blood work and wondered, “Does psoriasis affect white blood cells?” the answer is yes. Psoriasis can change your white blood cell (WBC) count, which your immune system relies on to fight off germs. If your WBC levels are too high or too low, you may get sick more often or have other symptoms.

Beyond psoriasis, other factors can cause an abnormal WBC count, including certain treatments or other health conditions. If a blood test shows your WBC count is off, your doctor can recommend options to help bring it back to a healthy range.

What Are White Blood Cells?

WBCs are also called leukocytes. These immune system cells travel through your blood and help your body fight infections and heal injuries.

There are five main types of WBCs:

• Neutrophils — Defend against infections and repair damaged tissues
• Lymphocytes — Include T cells and B cells, fight infections, and make proteins called antibodies that help recognize foreign invaders
• Basophils — Trigger allergic responses
• Eosinophils — Fight parasites, cancer cells, and help produce allergic responses
• Monocytes — Clear away damaged or infected cells

Measuring White Blood Cells

Your doctor can check your WBC count with a blood test called a complete blood count (CBC). A CBC usually shows only your total WBC. But if your doctor orders a test called a differential, it will break down the count of each type of WBC in your blood.

A CBC may show that you have leukocytosis, which means your WBC count is high. Leukocytosis can be a sign of inflammation and can happen for many reasons, such as:

• Infection
• Allergies
• Excess stress
• Thyroid issues
• Immune disorders, such as rheumatoid arthritis or lupus
• Some medications, such as corticosteroids

A CBC may also reveal that you have leukopenia, which means low levels of WBCs. Usually, leukopenia refers specifically to a lower-than-normal number of neutrophils. It may be caused by:

• Autoimmune disorders
• Bone marrow disorders, such as multiple myeloma
• Infection, such as human immunodeficiency virus (HIV)
• Certain medications
• Vitamin deficiency and/or malnutrition

If you have leukopenia, you may have an increased risk of infections. Your doctor may do more tests to find out what’s causing the low WBC count.

How Can Psoriasis Affect White Blood Cells?

WBCs travel through your bloodstream, looking for anything that doesn’t belong — like germs or damaged cells, including cancer cells. Think of them as soldiers on constant patrol. When they find a threat, they attack it to protect your body and keep you healthy.

In autoimmune conditions like psoriasis, WBCs mistakenly recognize healthy cells as foreign invaders and attack them. In psoriasis, a type of WBC called a T cell targets skin cells. This triggers inflammation and leads to discolored, itchy, and flaky patches on the skin. T cells release cytokines, which are small proteins that help immune cells communicate with each other. These cytokines signal other WBCs, especially neutrophils, to come to the area. Neutrophils also release cytokines and other chemical signals that increase inflammation in psoriasis.

Psoriasis and High White Blood Cell Count

Have you ever wondered, “Can autoimmune disease cause high white blood cell count?” Inflammation from an autoimmune disease can cause your body to make more WBCs. Because psoriasis flare-ups involve inflammation, it makes sense that people with the condition often have leukocytosis. Researchers have found that levels of neutrophil activity, in particular, are commonly higher in people with psoriasis.

A high WBC count can sometimes be a sign of cancer, but this doesn’t happen often. People with psoriasis have a slightly higher chance of developing certain cancers, especially lymphoma (a type of blood cancer) and some skin cancers. The risk may be higher in people with severe psoriasis than in those with milder forms. Scientists aren’t sure why psoriasis raises the risk of lymphoma, but it may be linked to long-term immune system activity.

Psoriasis and Low White Blood Cell Count

Psoriasis may be connected to lower-than-normal WBC counts. Researchers have found that people with psoriasis may have slightly decreased levels of lymphocytes. Scientists don’t know why exactly this happens, but it could be related to T-cell involvement in causing inflammation or psoriasis medications.

Psoriasis and Neutrophil-to-Lymphocyte Ratio

Your doctor may use the results of your WBC count to calculate a neutrophil-to-lymphocyte ratio (NLR). Studies have found that this ratio is commonly higher in people with psoriasis. Researchers are currently investigating whether the NLR could help diagnose different types of psoriasis and assess how well your psoriasis treatment is working.

Can Psoriasis Medications Affect White Blood Cell Counts?

Biologics are medicines made from living cells that help control the immune system. The side effects of some oral treatments and biologics used to treat psoriasis and psoriatic arthritis can also affect WBC counts. If you’re taking medicine to treat psoriasis, your dermatologist will check your WBC count to make sure it stays in a healthy range.

Oral Treatments and White Blood Cells

Psoriasis oral treatments are small-molecule drugs that target your immune system to decrease inflammation caused by psoriasis. These medications can affect your WBC count by suppressing your immune system.

Up to 25 percent of people who take retinoids — medications made from vitamin A that help slow skin cell growth — may have a small increase or decrease in their WBC count. Other oral treatments called immunosuppressants can also affect WBC levels. These drugs may cause leukopenia.

Newer oral medications include phosphodiesterase 4 (PDE4) inhibitors and tyrosine kinase 2 (TYK2) inhibitors. They work to block certain chemical pathways in the body that can make psoriasis worse. PDE4 inhibitors don’t usually change the WBC count, but mild leukopenia sometimes develops. TYK2 inhibitors may lower your lymphocyte counts a little, so your doctor should watch you as they would with any other medication that affects your immune system.

Biologic Treatments and White Blood Cells

Biologic treatments are protein-based drugs given by an injection into the skin or vein that target specific parts of the immune system. Biologics for the treatment of psoriasis are also associated with a minor decrease in WBC count, especially a decrease in neutrophils.

Some psoriasis medications are designed to block interleukin-17 (IL-17) — a protein mostly made by neutrophils. A 2021 study found that these medications may lower both neutrophil counts and the total number of WBCs in people with psoriasis. Other IL-17 blockers may affect how neutrophils behave in the body or change your WBC levels.

Other medications work by targeting interleukin-23 (IL-23). These medications don’t often change someone’s WBC count, but leukopenia is occasionally a side effect.

Researchers have also seen lower neutrophil and leukocyte counts in people taking medications that block both IL-12 and IL-23.

Other biologics work by blocking a protein in the body called tumor necrosis factor-alpha (TNF-alpha). Sometimes, these drugs may cause your neutrophil count to drop a little.

Biologic medications usually lower WBC counts. But in people with lymphoma, they may do the opposite. In the past, some studies suggested that TNF-alpha inhibitors and other biologic medications might raise the risk of lymphoma and other cancers. Newer research shows this may not be the case. Instead, it may be the uncontrolled inflammation from psoriasis that raises cancer risk.

All medications, even those you can buy without a prescription, can cause side effects. Your doctor will help you look at the possible benefits and risks of each treatment option.

Symptoms of High or Low White Blood Cell Count

Talk to your doctor or dermatologist about how often you should have a CBC blood test to check your WBC count. The frequency may be different depending on how severe your psoriasis is, which medications you’re taking, and what symptoms you have.

Not everyone with a high or low WBC count will have symptoms. Symptoms of either a high or low WBC count can include:

• Fever
• Wounds that don’t heal
• Frequent illness
• Unexplained cough that doesn’t go away
• Easy bruising
• Mouth sores

Talk to Your Doctor

Because symptoms like fever, slow-healing wounds, or frequent illness can also be caused by an infection or another health problem, it can be hard to know if they’re related to changes in your WBC count. If you’re concerned about any of these issues, talk to your doctor. A blood test is the only way to know for sure if your WBC count is outside the normal range.

Find Your Team

On MyPsoriasisTeam, the social network for people with psoriasis and their loved ones, members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis.

Have your WBC counts changed since you were diagnosed with psoriasis? Share your experience in the comments below, or start a conversation by posting on your Activities page.