I'm not sure wether this belongs in guide or exploit but I'm quite certain this is not intended.
Screenshot
Just stand on the cannon shown in the picture and you will avoid the aura completly altough you will still take damage when he throws the food on you.
EDIT: To clarify: Cookie throws rotten food on you, it emits an aura which causes 10k damage if you stand in it, by standing on the canon, you will still be hit when he throws the food which causes roughly 5.5k dmg but the food lands under the canon nullifying the aura.