From Nookipedia, the Animal Crossing wiki
Medicine is an item in the Animal Crossing series from Dōbutsu no Mori e+ and onward. It can be purchased at Tom Nook's Store for 400 bells (1,200 in Dōbutsu no Mori e+). Medicine can heal sick villagers and cure bee stings. A villager's sickness may last a week and sometimes even longer. If the player provides medicine for the sick villager, he she will give the player an item for gratitude after being cured, as well as a verbal praise after each dose received. Any players can give medicine, and the player who contributed the most medicine will receive the gift.
In Animal Crossing: New Leaf, any villagers who have a friendship with the player will supply medicine to the player if he or she is stung by a bee.
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