Unit Converter
Immunoglobulin E (IgE)
Synonyms
- IgE
- Total IgE
- Serum IgE
- Reagin
- Type I hypersensitivity antibody
- Atopy marker
Units of Measurement
- IU/mL
- ng/mL
- ng/dL
- ng/100 mL
- ng%
- µg/L
Key Conversions
1 IU/mL ≈ 2.4 ng/mL
1 ng/mL ≈ 0.417 IU/mL
1 µg/L = 1 ng/mL
1 ng/dL = 0.01 ng/mL
ng% = ng/dL = ng/100 mL
Description
Immunoglobulin E (IgE) is the least abundant serum immunoglobulin, but plays a central role in allergic reactions.
Produced by:
- Plasma cells in mucosal & lymphoid tissues
IgE binds with high affinity to:
- Mast cells
- Basophils
Exposure to allergens cross-links IgE → mast cell degranulation → release of:
- Histamine
- Leukotrienes
- Prostaglandins
Resulting in Type I hypersensitivity reaction.
Physiological & Immunological Role
1. Allergy & Atopy
Key mediator of:
- Allergic rhinitis
- Asthma
- Atopic dermatitis
- Food allergy
- Drug allergy
- Anaphylaxis
2. Defense Against Parasites
Important in:
- Helminth infections
- Eosinophil activation
- Mucosal immune response
3. Immunoregulation
IgE helps modulate immune signaling and Th2 pathways.
Clinical Significance
Elevated IgE (Hyper-IgE)
1. Atopic Diseases
- Allergic asthma
- Allergic rhinitis
- Eczema
- Food allergies
- Drug allergies
- Urticaria and anaphylaxis
Typically: 100–1000 IU/mL, but may exceed 2000 IU/mL in severe atopy.
2. Parasitic Infections
Especially helminths:
- Strongyloides
- Ascaris
- Schistosoma
- Hookworm
Often >1000 IU/mL.
3. Hyper-IgE Syndrome (Job’s Syndrome)
Very high IgE:
- >2000 IU/mL (often >5000 IU/mL)
Clinical features: - Recurrent skin abscesses
- Pneumonias
- Eczema
- Eosinophilia
- Skeletal abnormalities
Genetic: STAT3 or DOCK8 mutations
4. IgE Myeloma (rare)
Monoclonal IgE spike.
5. Immunodeficiency Conditions
- Wiskott–Aldrich syndrome
- Omenn syndrome
6. Smoking
Moderate elevation due to airway irritation.
Low IgE
Conditions:
- Common Variable Immunodeficiency (CVID)
- X-linked agammaglobulinemia
- Selective IgE deficiency (rare, asymptomatic)
- Immunosuppressive therapy
Low IgE alone is usually not clinically concerning.
Reference Intervals
(Tietz 8E + Mayo + ARUP + AAAAI)
IgE reference ranges are age-dependent and vary widely.
Total Serum IgE
| Age | IgE (IU/mL) |
| 0–1 year | 0 – 15 |
| 1–5 years | 0 – 60 |
| 6–9 years | 0 – 90 |
| 10–15 years | 0 – 200 |
| Adults | 0 – 100 (some labs 0–150) |
High IgE thresholds
- >150 IU/mL → suggests atopy
- >1000 IU/mL → severe allergy or parasitic infection
- >2000 IU/mL → consider hyper-IgE syndrome
Diagnostic Uses
1. Atopic Disease Evaluation
Elevated IgE supports:
- Asthma
- Atopic dermatitis
- Allergic rhinitis
- Food/drug allergies
Total IgE helps guide:
- Severity
- IgE-mediated nature
- Eligibility for anti-IgE therapy (omalizumab)
2. Parasitic Infection Screening
Markedly high IgE with eosinophilia is suggestive.
3. Hyper-IgE Syndrome Diagnosis
IgE >2000 IU/mL + recurrent infections.
4. IgE Myeloma Evaluation
Serum electrophoresis + IgE quantification.
5. Immunodeficiency Assessment
Low IgE contributes to the immunoglobulin profile for:
- CVID
- Agammaglobulinemia
- Combined immunodeficiency
6. Omalizumab (Anti-IgE Therapy) Dosing
Total IgE determines:
- Patient eligibility
- Dose range
- Treatment adjustments
Analytical Notes
- Serum preferred
- Non-IgE allergies may have normal IgE
- Very high IgE (>5000 IU/mL) may cause hook effect-lab must dilute sample
- IgE is stable at room temperature for short periods
- Measured by immunoassays (fluoroenzyme, chemiluminescence)
Clinical Pearls
- Total IgE is not diagnostic for any specific allergy - must be paired with specific IgE testing.
- Atopic dermatitis often shows extremely high IgE levels (>2000 IU/mL).
- High IgE in asthma can qualify for biologics (anti-IgE therapy).
- IgE may remain high even when symptoms improve.
- Normal IgE does not rule out allergic disease (e.g., non-IgE-mediated food allergies).
Interesting Fact
IgE is the least abundant immunoglobulin in serum (<0.001% of total Ig), yet drives some of the strongest immune reactions, including anaphylaxis.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Immunoglobulins.
- AAAAI / WAO Allergy Practice Parameters.
- Mayo Clinic Laboratories - IgE.
- ARUP Consult - Allergic & Immunodeficiency Testing.
- EAACI Guidelines on IgE-mediated disease.
- MedlinePlus / NIH - IgE Test.