<prompt> Skin test demonstrates all types of hypersensitivity except:Type 1Type 2Type 3Type 4  <response>: Ans: b type 2Ref: Kubys Immunology, 6th ed. Pg. 371-396.Hypersensitivity Type I hypersensitivity - Ig E mediated- Causes systemic anaphylaxis and localized atopy- Detection includes skin testing by intradermal injection or by superficial scratching which helps in screening of allergens Type II hypersensitivity- antibody mediated cytotoxicity- Causes transfusion reactions, haemolytic disease of newborn, drug induced haemolytic anaemia etc- No skin test is used for detection Type II hypersensitivity- immune complex mediated- Causes arthus reaction and serum sickness- It can be as a result of injection of antigen Type IV hypersensitivity - delayed type- Contact dermatitis, granuloma etc- Can be detected by skin tests and patch tests. 