Your health history and symptom description are usually enough for your doctor to make a diagnosis of chronic hives. However, they may also perform tests to confirm the diagnosis or rule out other causes. This is because there are other conditions that can cause hives.
The most common tests during diagnosis include:
- Blood tests
- Skin biopsies
- Allergy tests
Blood tests
There are 4 common blood tests that doctors often use to diagnose chronic hives or rule out other conditions.
Complete blood count (CBC)
The CBC is a group of tests that assess the cells that circulate in your blood. This includes red blood cells, white blood cells, and platelets. The test uses a blood sample drawn from a vein in your arm.1
People with chronic hives have a higher risk of low levels of eosinophils. These are white blood cells involved in allergic reactions. Low eosinophil levels are linked to worse symptoms and poor response to antihistamines. High eosinophil levels may be a sign of another skin condition or a parasitic infection.2,3
C-reactive protein (CRP) test
This test measures the amount of C-reactive protein (CRP) in your blood. CRP is a protein that increases when there is inflammation in your body. A simple blood draw can measure CRP levels.4
Most people with chronic hives have normal CRP levels. High CRP levels are linked to worse symptoms, lower quality of life, and poor response to antihistamines. High levels may prompt your doctor to test for other autoimmune or infectious conditions.5,6
Erythrocyte sedimentation rate (ESR or sed rate)
This test measures how fast red blood cells (erythrocytes) fall in a blood sample in a test tube. Normally, red blood cells fall relatively slowly. When there is more inflammation, your red blood cells fall faster because of high protein levels. A simple blood draw can measure ESR.7
Most people with chronic hives have a normal ESR. A high ESR is linked to worse symptoms, lower quality of life, and poor response to antihistamines. High ESR may be a sign of autoimmune or infectious conditions.3
Thyroid-stimulating hormone (TSH) levels
TSH is a hormone that tells your thyroid to make other hormones that control metabolism. Testing TSH levels in your blood can show how well your thyroid is working. High TSH levels may be a sign of an underactive thyroid (hypothyroidism). Low levels may mean it is overactive (hyperthyroidism).8
Experts do not recommend routinely measuring TSH levels in people with chronic hives. However, there is a link between chronic hives and thyroid autoimmune conditions. This is why some doctors choose to test TSH in adults with chronic hives. They may perform other thyroid tests if TSH levels are abnormal.9
Skin biopsy
A skin biopsy is a procedure where doctors remove a small sample of your skin. They will then check the skin under a microscope to diagnose skin conditions. Doctors usually do not need a skin biopsy to diagnose chronic hives. However, they may use it to rule out other conditions.3,10
If you have any signs of other conditions, such as urticarial vasculitis or mastocytosis, your doctor may perform a punch biopsy. In this procedure, your doctor will use a circular tool to remove a small portion of newly formed hives. You may need to stop taking certain medicines before the test.3
Allergy tests
Allergic reactions are a common cause of acute hives, not chronic hives. This is why allergy tests are not routinely done for people with chronic hives.11
However, if your health history suggests that a certain trigger causes hives, your doctor may perform allergy tests. These may include:11
- Skin prick tests – Testing allergens on your skin to see if your skin turns red or swells
- Blood tests – Checking for specific allergy-related antibodies in your blood
Knowing what allergens trigger hives can help you avoid exposure. This can help improve symptoms and reduce the need for medicine.
Autoimmune condition tests
In autoimmune conditions, your body makes antibodies that mistakenly attack healthy cells. ESR and CRP are indirect tests for autoimmune conditions. Other blood tests for autoimmune conditions measure the levels of certain antibodies in your blood. For example, the antinuclear antibody (ANA) test is often used to diagnose lupus.12
Hives may be a symptom of an autoimmune condition, such as lupus. However, doctors do not usually test for autoimmune conditions unless your health history suggests an autoimmune reaction.3