An allergy is a condition caused by exposure, inhalation, or ingestion of something that results in particular symptoms.
In mainstream Smurfs media, Sickly claims to have various types of allergies. Jokey in the cartoon show episode "Calling Dr. Smurf" does have a real allergy to pink paint, which Dabbler treated with skin cream. Papa Smurf in the episode "The Sky Is Smurfing" has an allergic reaction to volcanic dust, which Brainy mistakes for having a cold.
In "Gargamel's New Job," Prince Theodore reveals that he is allergic to chicken feathers after his newly-hired Court Magician, Gargamel, accidentally summons a feather storm. Also, in the episode, "The Clumsy Genie", the prince is also allergic to feathers.