What is IgE?
Immunoglobulin E (IgE) is an antibody class produced by plasma cells (immune cells) in response to allergens — substances the immune system mistakenly identifies as threats, such as pollen, pet dander, dust mites, foods and insect stings. IgE binds to mast cells in tissues. When the allergen is encountered again, IgE triggers mast cell degranulation — the release of histamine and other chemicals that cause allergy symptoms. Total serum IgE gives a general picture; specific IgE tests (also called RAST or ImmunoCAP) identify which specific allergens you are sensitised to.
Total IgE normal range
| Age | Normal Total IgE (IU/mL or kU/L) |
|---|---|
| Adults | < 100 IU/mL (some labs up to 150) |
| Children (2-10 yrs) | < 100 IU/mL |
| High allergy load | 100 – 500 IU/mL |
| Very high | > 500 IU/mL (consider parasites, atopic disease) |
| Hyper-IgE syndrome | > 2,000 IU/mL |
Causes of high total IgE
| Condition | IgE Level | Notes |
|---|---|---|
| Allergic rhinitis (hay fever) | Mildly elevated | Specific IgE to pollen positive |
| Asthma (allergic) | Mildly-moderately elevated | Inhaled allergens trigger attacks |
| Atopic dermatitis (eczema) | Often very high | Skin barrier dysfunction and allergy |
| Food allergy | Mildly-moderately elevated | Specific IgE to foods (peanut, milk, egg etc.) |
| Parasitic infections (worms) | Very high | Key cause in tropical regions |
| Allergic bronchopulmonary aspergillosis (ABPA) | Very high | Fungal allergy in lungs |
| Drug allergy | Variable | Some drug reactions are IgE-mediated |
Specific IgE testing (RAST / ImmunoCAP)
Specific IgE tests measure IgE antibodies against individual allergens in a blood sample. Common panels include: respiratory (dust mite, grass pollen, cat/dog dander, mould), food (peanut, tree nuts, milk, egg, wheat, shellfish), insect sting (bee, wasp) and latex. Results are reported in classes from 0 (not detected) to 6 (very high). Class ≥2 is typically considered clinically relevant.
Questions to ask your doctor
- Should I have a specific IgE panel to identify my trigger allergens?
- Do I need a skin prick test as well?
- Could a parasitic infection be causing my high IgE?
- Am I a candidate for immunotherapy (allergy shots or sublingual drops)?
- Should I carry an adrenaline (epinephrine) auto-injector?