Answer: sound.
Explanation: an argument is sound when it is valid (if the premises are true, then the conclusion is also true) and the premises are true. It is unsound it is doesn't have one of those two characteristics. In the given statement, the premise is "I am allergic to peanuts" and the conclusion is "I do not eat peanut butter," this argument is valid, because if the premise is true, then the conclusion is also true, and we don't have any reasons to believe that the premise isn't true, so the argument is sound.