Anaphylaxis is caused by-: (A) N2O, (B) Althesin, (C) Halothane, (D) Propofol
Answer is B. (Refer: Morgan and Mikhail’s Clinical Anaesthesiology, 5th edition)
Althesin

Althesis is a neurosteroid
It was used as a parenteral anaesthetic
It was withdrawn from the market because of several severe anaphylactic reactions