Common Blood Tests for Eczema: What They Reveal About Your Skin Condition

Eczema, or atopic dermatitis, is a common chronic skin condition characterized by dry, itchy, and inflamed skin. It is increasingly common in children, but it can also affect adults. Eczema usually requires medical management as it can lead to recurrent infections and can massively impact a person’s quality of life if not properly managed.

Atopic dermatitis is a specific type of eczema that is associated with immune dysregulation.  It is closely linked to allergies, and it’s considered part of the “allergic triad,” which also includes asthma and allergic rhinitis. 

Eczema is primarily a clinical diagnosis based on symptoms like itchy, red rashes and potential skin thickening from chronic scratching. The rash commonly appears in flexural areas (like inner elbows and knees) in older children and adults, and on the face in infants. 

While eczema is primarily a clinical diagnosis, blood tests can provide valuable insight into the processes driving eczema flare ups.

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Why Blood Tests are Used in Eczema Diagnosis

Blood tests can help rule out other conditions that mimic eczema, like infections or autoimmune disorders, and identify potential allergens through specific IgE testing. IgE tests measure total IgE levels and specific allergen-related IgE antibodies, indicating an atopic response typical of eczema.

They can also measure specific inflammation markers and eosinophil counts to help clinicians understand the process behind a patient’s flare and remission cycles. These insights help guide treatment decisions, such as whether further allergy testing is needed for avoidance strategies.

However, blood tests are not standalone diagnostic tools for eczema; they complement clinical assessments based on patient history, physical examination, and symptom presentation. Blood tests are often considered to provide insight into severe or difficult cases.

Eczema and Autoimmune Disease

Eczema is not an autoimmune condition, although a systematic review and meta-analysis involving over 90 million patients showed a clear link between eczema and the development of certain autoimmune conditions, likely due to immune dysregulation and shared genetic links. 

Blood tests can clarify the pathogenesis behind eczema in some patients (elevated IgE levels), and may reveal early autoimmune patterns that can signal a need for intervention to reduce the risk of developing an autoimmune condition.

Common Blood Tests for Eczema

Here are the most common blood tests ordered for eczema:

Total IgE (Immunoglobulin E) Test

IgE antibodies play a key role in the immune response to allergens. In eczema, there is often an overproduction of IgE, leading to an overactive immune response to triggers like pollen, dust mites, or certain foods. This IgE-mediated response causes skin inflammation, barrier damage, dryness, itchiness, and increased infection risk.

While elevated total IgE levels are common in eczema, they are not specific to the condition and can also be seen in other atopic disorders, parasitic infections, cancers, and some autoimmune diseases. Therefore, total IgE testing should be interpreted in the context of a patient’s comprehensive medical evaluation.

Specific IgE (Allergen-Specific Test)

RAST (radioallergosorbent test) and ImmunoCAP tests measure specific IgE antibodies in the blood to identify allergen triggers like pollen, dust mites, and foods such as wheat, eggs, peanuts, soy, and dairy. 

ImmunoCAP, a second-generation test, offers better sensitivity, specificity, and broader allergen detection than RAST. These tests help pinpoint triggers that exacerbate symptoms, aiding in management plans, and are useful when skin tests aren't feasible. However, they can be inaccurate up to 60% of the time, requiring professional interpretation alongside the patient's medical history. 

While helpful, these tests are not definitive for diagnosing eczema, which relies primarily on clinical evaluation. Elevated IgE levels are common but not exclusive to eczema, as some atopic patients show normal IgE levels.

Complete Blood Count (CBC)

A Complete Blood Count (CBC) measures red blood cells, white blood cells, and platelets. It provides important information about the overall health of a patient and can help detect a range of conditions, from infections to immune system disorders.

A CBC can reveal signs of inflammation or infection by measuring the levels and types of white blood cells (WBCs) in the blood. Elevated WBC counts, particularly of neutrophils or lymphocytes, can indicate an ongoing infection or inflammatory response, suggesting that the body's immune system is actively fighting off a pathogen or reacting to inflammation.

Complete blood count (CBC) tests also include eosinophil counts, which are a straightforward way to assess the level of eosinophilia in eczema patients. The degree of eosinophilia can illustrate the severity of a patient’s allergic response. 

Eosinophil Count

Eosinophils are white blood cells involved in the immune response, especially during allergic reactions and parasitic infections. Too many eosinophils cause inflammation, leading to itching, redness, and swelling.

High eosinophil levels are common in conditions like asthma and eczema, indicating a stronger allergic response. This can worsen inflammation, skin barrier dysfunction, and itching, making eczema more severe and persistent.

In eczema, increased Th2 (a type of white blood cell) activity during acute flare ups elevates IL-5 which promotes eosinophil production, activation, and migration to the skin.

Blood tests measuring eosinophil counts can help assess the allergic component of eczema. High eosinophils may signal a need for further allergen testing.

C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR)

CRP and ESR are blood tests that detect inflammation. CRP measures a protein produced by the liver, while ESR assesses how quickly red blood cells settle; inflammation causes red blood cells to become “sticky,” causing cells to stick together in heavy clumps that settle faster.

CRP rises quickly during acute inflammation or infection, while ESR increases more gradually, reflecting chronic inflammation and ongoing disease activity.

CRP and ESR tests help gauge eczema severity and monitor treatment response, with higher levels indicating more severe inflammation.

When Are Blood Tests Necessary for Eczema?

Blood tests are generally reserved for more severe or complex cases of eczema that do not respond well to standard treatments. They can provide valuable information about underlying factors that may be contributing to the condition, such as immune system dysfunction or chronic inflammation.

Blood tests are also recommended when the diagnosis of eczema is unclear, when a patient experiences persistent or frequent flare-ups, or when there is a suspicion of underlying allergies that could be exacerbating the condition. They help to identify specific allergens, infections, or other triggers that might not be apparent through a physical examination alone.

Guiding Long-Term Treatment and Identifying Co-existing Conditions

Blood tests are important for creating a targeted, long-term treatment plan. They can help in monitoring the effectiveness of treatments, adjusting medications, and managing symptoms more effectively. 

Additionally, they can identify co-existing conditions such as asthma, allergic rhinitis, or other atopic disorders that often accompany eczema, allowing for a more comprehensive approach to patient care.

Understanding Blood Test Results: What They Mean for Your Eczema

High, normal, and low values in blood tests can indicate different aspects of eczema and its severity. Elevated levels of markers like eosinophils, IgE, or CRP suggest an active allergic or inflammatory response while normal values may indicate controlled inflammation.

‍Elevated eosinophils and IgE levels may also predict treatment response and guide management decisions.

The finding of elevated CRP, with or without elevated ESR, alongside normal eosinophils should prompt consideration of an active infection.  

Blood test results should be evaluated by a dermatologist or allergist, who can provide insights based on their expertise, and as part of the patient's clinical symptom picture and medical history to ensure accurate diagnosis and effective management of eczema.

How Blood Test Results Can Influence Treatment Plans

Blood tests can guide management strategies, especially in complex or severe cases of eczema. 

Customization Based on Allergens 

Identifying specific allergens through blood tests allows for personalized treatment strategies such as avoiding certain triggers, starting allergy shots, or adjusting dietary habits.

Guiding Medication Use

Elevated inflammation markers may prompt the use of corticosteroids, immunosuppressants, or biologics to reduce inflammation and control eczema. Blood tests help determine the most appropriate medication and dosage.

Adapting Long-Term Management

Regular monitoring of blood test results allows healthcare providers to adjust treatment plans over time, aiming for better long-term control of eczema and minimizing flare-ups.

What to Expect During Blood Testing for Eczema

Blood testing is actually a simple, straightforward process with minimal discomfort. If you are bringing your child in for blood tests, plan to bring books and toys as distractions, and try to schedule something fun or rewarding for the child after the procedure.

Overview of the Process

Blood tests for eczema typically involve a simple blood draw, usually from a vein in the arm. Fasting is not required, but your doctor will provide specific instructions if it is needed. 

Medications like antihistamines generally do not need to be avoided prior to testing, although it is important to confirm this with the ordering provider. 

Some patients may experience mild discomfort or a slight pinch when the needle is inserted. To prepare, staying hydrated and relaxed can make the process smoother.

Receiving Results

Blood test results are generally available within a few days. Once results are in, a follow-up appointment with your healthcare provider will help interpret the findings and discuss any necessary changes in your treatment plan.

When to Discuss Blood Tests with Your Doctor

Consider asking your doctor about blood tests if you experience persistent symptoms, frequent eczema flare-ups, or suspect specific triggers such as allergens that might be contributing to your condition.

Your doctor may recommend a referral to a dermatologist or an allergist for expert assessment of your blood test results. They are best equipped to interpret these results, ensuring a more accurate diagnosis and effective treatment plan.

Follow-up appointments are required to discuss blood test results. These sessions allow your doctor to explain what the results mean, adjust your treatment plan accordingly, and ensure your eczema is managed effectively over the long term.

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Key Takeaways

• Blood tests such as total and specific IgE, complete blood count (CBC), CRP, and ESR provide insights into allergic responses and inflammation associated with eczema, helping to guide diagnosis and treatment plans.

• Patients should stay informed about their condition and discuss blood test options with healthcare providers, as these tests can help pinpoint triggers and monitor the effectiveness of treatments.

• While not definitive, blood tests are valuable tools in the comprehensive management of eczema, aiding in identifying co-existing conditions and guiding personalized treatment strategies.