Drugs.

[DracIV]

"People are also allergic to peanuts, but that doesnt mean they should make Peanut M&Ms illegal."

Jewpin, there is a big difference. Peanut M&Ms don't naturally spread out and enter your body without you even knowing it sometimes. Smoke of any sort spreads out and can enter your body on its own. Peanut M&Ms can be refused, holding you breath against a smoke to may not see is a bit hard if it takes multiple minutes to be sure you passed.