The Casoni's test is an immediate hypersensitivity test originally introduced by Casoni in 1911. The antigen in hydatid fluid collected from animal or human cysts and sterilised by Seitz or membrane filtration and is injected (0.2 ml) intradermally on one arm and an equal volume of saline as control on the other arm. In positive cases a large wheal, about 5 cm in diameter, with multiple pseudopodial projections appears within 20 to 30 minutes at the test site and fades in an hour. A secondary reaction consisting of oedema and induration appears after 8 hours. The test is very sensitive, but not specific and false-positive reactions may appear in a number of other conditions. Casoni's test is little used now and has been supplanted by serological tests. REF:TEXTBOOK OF MEDICAL PARASITOLOGY;CKJ PANIKER;8TH EDITION;PAGE NO 134