This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Anaphylaxis is caused by- 
Select and explain. 
A. N2O, B. Althesin, C. Halothane, D. Propofol
B: Althesin
Answer: B: Althesin 
Explanation: (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It was withdrawn from the market because of several severe anaphylactic reactions