Step 1: Understanding the Concept
Analgesics relieve pain without affecting consciousness.
Step 2: Check Each Option
BHT and gallic acid are antioxidants used as food preservatives.
Curcumin is a natural colouring and antiseptic compound.
Methyl salicylate (oil of wintergreen) is used as a pain reliever.
Step 3: Compare the options
Methyl salicylate is option (B).
Final Answer:
Methyl salicylate is used as an analgesic.
\[ \boxed{\text{(B) }\text{Methyl Salicylate}} \]