Allergy test: Skin Prick Tests

Allergic symptoms can be caused by different immunological mechanisms. The majority of allergic diseases are caused by either the Type I (or immediate-type) hypersensitivity response, or the Type IV (or delayed-type) hypersensitivity response. The type of tests needed to diagnose allergy depends on the type of allergic reaction being investigated.

Immediate-type hypersensitivity reactions are caused by antibodies called IgE produced by the immune system against allergens such as pollens, house dust mites, mold spores, animal dander, insect venom, food or drugs. When you are exposed to these allergens, the IgE attached to allergy cells called mast cells binds to the allergens and trigger the mast cells to release chemical mediators such as histamine. This leads to swelling, itching, redness, congestion and airway constriction within a matter of minutes.
IgE antibodies are involved in causing nasal and ocular allergies, asthma, insect sting allergies and some types of food and drug allergies.
Skin prick tests involve the introduction of a tiny amount of allergens into the surface layer of the skin, where there is a rich source of mast cells. A small swelling surrounded by redness will appear after 15 minutes if there is sensitivity to the allergens. The video above shows how this is done.

Skin prick tests are quick, safe and accurate. A large variety of allergenic extracts are commercially available for testing. However, the skin must be in good condition and the patient must not have taken antihistamines beforehand. Patients with active dermatitis or urticaria (hives) should not be tested because increased skin sensitivity might result in false positive results. 


Reference information:  www.allergy.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.