Immunoglobulin E (Total)
IgE· also: Total IgE, Serum IgE
Clinical Overview
Total IgE measures the total amount of IgE immunoglobulin in the blood. IgE is the antibody class responsible for immediate hypersensitivity reactions (Type I allergy). It binds to mast cells and basophils; when allergen cross-links IgE on these cells, histamine and other mediators are released — causing allergic symptoms. Elevated IgE is seen in atopic conditions and parasitic infections.
Why This Test Matters
Total IgE has limited clinical utility on its own because normal ranges are wide and IgE can be elevated in many non-allergic conditions. Total IgE is most useful when markedly elevated (>1000–2000 IU/mL) — which strongly suggests allergic disease or parasitic infection. For specific allergy testing, specific IgE antibodies (formerly called RAST) to individual allergens (dust mites, pollen, food proteins, latex) are far more informative. Total IgE is used in the Asthma Predictive Index and is measured before prescribing omalizumab (anti-IgE therapy) to determine eligibility and dosing.
Reference RangesWHO/IFCC standards
| Age Group | Reference Range | Unit | Notes |
|---|---|---|---|
| Adults (18–64) | 0 – 100 | IU/mL | Adult normal; varies with age |
| Children / Pediatric | 0 – 60 | IU/mL | Children; lower thresholds |
Also reported in: kU/L.
What Causes Abnormal Results?
High IgE Causes
- Allergic asthma, allergic rhinitis (hay fever), atopic dermatitis (eczema)
- Food allergy (peanut, milk, shellfish, etc.)
- Parasitic infections (helminths: roundworm, hookworm, Toxocara — often cause very high IgE)
- Allergic bronchopulmonary aspergillosis (ABPA) — very high IgE >1000 IU/mL
- Hyper-IgE syndrome (Job's syndrome) — IgE >2000 IU/mL with eczema, recurrent staphylococcal abscesses
- Wiskott-Aldrich syndrome
- Churg-Strauss syndrome (eosinophilic granulomatosis with polyangiitis)
Low IgE Causes
- Congenital hypogammaglobulinemia (IgG, IgA, IgM deficiency — IgE also low)
- Non-atopic individuals (naturally low IgE in people without allergic tendencies)
Signs & Symptoms to Watch For
How to Prepare for This Test
No fasting required. Total IgE is measured by immunoassay from a routine blood sample. Elevated IgE should prompt specific allergen testing (specific IgE panels) and allergy specialist evaluation.
Factors That Can Affect Results
- Age (IgE naturally rises through childhood, peaking in teens, then declining in adults)
- Smoking (cigarette smoking raises total IgE)
- Active eczema flare (raises total IgE)
- Parasitic infection (can massively elevate IgE — always consider in returning travelers or migrants)
- Time of year (seasonal allergen exposure can temporarily raise IgE)
Related Topics
Frequently Asked Questions
What is the difference between total IgE and specific IgE?
Total IgE measures all IgE in the blood regardless of what it targets — it just tells you the overall "allergy burden." Specific IgE (formerly RAST or ImmunoCAP) measures IgE directed against one particular allergen — such as cat dander, peanut protein, or house dust mite. Specific IgE is far more clinically useful for allergy diagnosis and guiding allergen avoidance. Total IgE mainly helps interpret specific IgE results (a high total IgE context makes borderline specific IgE results less meaningful) and is used before prescribing omalizumab.
Can I use IgE to diagnose food allergies?
Total IgE alone cannot diagnose food allergies. Specific IgE to the food of concern (e.g., peanut-specific IgE, milk-specific IgE) is needed. Even specific IgE results must be interpreted with clinical history — a positive specific IgE means sensitization (the immune system has made IgE to that food) but not necessarily clinical allergy. Oral food challenges under medical supervision remain the gold standard for food allergy diagnosis. See an allergy specialist for comprehensive evaluation.