Blood tests for allergy:
The most commonly used blood test is specific IgE test previously known as RAST: (Radioallergosorbent Test).In addition to RAST, detection and quantitation of mast cell mediators such as tryptase, a useful marker for anaphylaxis, may be investigated. However, blood sample should be collected within 4 hours of symptoms.
Indirect ‘markers’ of allergic inflammation e.g., total IgE, total eosinophil count, may be elevated in allergic reaction though some other disorders do the same. On the contrary, an individual may suffer with an allergic disease without an increased level of IgE or eosinophil.