Total IgE level : Total serum IgE level is commonly raised above the normal range in atopic patients or those with parasitic infections. A high serum IgE  is not harmful.

Hyper IgE syndrome is a very rare immunodefiency ( < 1:100,000) in which serum IgE levels are typically above 2000 kU/L. If a patients has a very high IgE levels AND recurrent infections/abscesses, then referral to Immunology should be considered.

Specific IgE levels: Specific IgE testing measures the amount of serum IgE that binds to a specific allergen ( formerly known as RAST testing).

Specific IgE testing  should only be requested if a clinical reaction to that allergen is suspected. Screening for multiple allergens should not be undertaken. Patients with high total serum IgE levels often have low titre "false positive" specific IgE results, limiting the usefullness of this test in eg: eczema patients.

When to request allergy testing? If a patient gives a history to suggest acute allergic reaction after consumption of a specific food (eg: urticaria, angiodema, breathing difficulty or collapse, usually within 1 hour of consumption). Or develops typical allergic symptoms after exposure to animals, pollens, dust etc , please send a clotted blood sample to Immunology labs requesting specific IgE to that food or other triggering agent.