This chapter has cover diagnosis of different allergies. 11 well illustrated pictures and diagrams are included to show different tests for allergy and enzymatic reaction. Diagnosis of allergy with the help of history and different tests, e.g. patch test, skin prick test, basophil granulation, Currschmann’s spirals, Radioallergosben test, invitro nasal smear, monoclonal antibodies, provocation test, food challenges are described in detail. 24 references are given at the end of the chapter for further reading. References are mentioned in text at appropriate places for the benefit of readers.