The total IgE level is one of the most important indicators for detecting allergies, the higher concentration of IgE, the more severe the allergy.

So, what is IgE?

Immunoglobulin E (IgE) is an antibody that associated with immediate hypersensitivity (i.e. the allergic reaction in daily life). There’s five classes of immunoglobulins (G, M, A, D, E), IgE is normally present in the blood in very small amounts, which is inextricably linked to type I allergy.

Why do doctors ask patients with allergic diseases to check allergen-specific IgE instead of IgG and IgM when they go to the hospital?

Because IgE is involved in both phases of the typical mechanism of type I hypersensitivity, including initial response and re-response.

In the initial response phase, when the body is first exposed to allergen, the allergen enters the body and its components are presented by antigen-presenting cells to T cells, which in turn secrete factors to induce B cells to produce IgE antibodies corresponding to that allergen, which bind to the surface of effector cells (mast cells/basophils) and wait. At this point, the patient does not yet have any discomfort, but is only in a special pre-allergic state and needs to be in the re-response phase before he or she can have allergic symptoms.

When re-responding patients are exposed to the same allergens again, they enter the body and bind to IgE on the surface of the aforementioned effector cells, as these IgE antibodies are allergen-specific IgE that specifically recognize and bind to this allergen. The combination of allergen and IgE initiates the activation of effector cells to degranulate and release chemical transmitters such as histamine, leukotrienes, kinins, prostaglandin D2, etc. These chemical transmitters cause the patient to develop allergic symptoms such as itching of the skin mucosa, runny nose, sneezing, wheezing, and even hypotension and fainting. For example: the action of histamine, capillary dilation, bronchial smooth muscle contraction, spasm, mucus gland secretion is enhanced; kinins, leukotrienes, and prostaglandin D2 can also produce the same effect as histamine, and can stimulate nociceptive nerves to trigger pain.

IgE antibody test, also known as acute allergen testing or immediate allergy testing, includes 80 common allergens (20 inhalant allergens and 60 ingestive allergens).

List of common allergens

Food allergens : soy, fish, shrimp, crab, alcohol, artemisia, peanut, milk, mango ……

Inhalant allergens: paint, rubber, perfume, mold, willow wool, elm/poplar, pollen, dust mites, house dust, fungi, animal dander, feather down ……