Can you buy insect spray if you are under the age of 18?

it seems like a stupid question but they might think that I'm getting high off of it or something but they don't know the recent problem with GNATS that I have that are making me lose my mind! and yesterday I got carded and wasn't allowed to buy Mucinex DM even though they could see that I obviously had a cold and could barely talk... anyways i'd appreciate if you could answer the question.