Intradermal skin testing using sequentially lower concentrations of an antigen vaccine

There are many different blood tests, protocols, or challenge methods used to determine the substances to which a person is allergic or sensitive.  There are several different methods available at Breakspear Hospital.

A blood sample is required for a radioallergosorbent test (RAST). The RAST checks for the amount of specific IgE antibodies in the blood, which are present if there is a classic allergic reaction. 

Another method to test allergic or sensitivity reactions is a process called “low-dose immunotherapy”, also known as "provocation/neutralisation".  It involves intradermal skin tests where sequentially lower concentrations of an antigen vaccine are injected just under the first few layers of skin at 10 minute intervals until a satisfactory response is observed.  When a satisfactory response is attained, the concentration of antigen vaccine is the neutralising dose.  This method is more sensitive than the skin-prick test and usually provides more consistent results.

The elimination and challenge method may be used to determine allergies and sensitivities.  This method requires the patient to not be exposed to a suspected allergen for a period of time and then it is reintroduced and the patient’s reaction evaluated. See Rotation Diet for a suggestion of how to possibly reduce reactions by changing your diet.

To determine food sensitivities, as opposed to classic food allergies, the blood test called ALCAT has been shown effective. The ALCAT system was developed by AMTL Corp (American Medical Testing Laboratories). It is a patented blood test that objectively measures the blood cells’ reactions to a foreign substance under conditions designed to imitate what happens when the food is consumed.