Phenolic aromas and flavors such as medicinal, listerinelike, band-aidlike, etc. are most often caused by bacteria due to poor sanitation. Sometimes it is caused by using chlorinated water or improper rinsing of cleaners and sanitizers. Phenols can also be extracted from the grain husks if your sparge temperature is too high.
Always watch your sanitation procedures throughout the process. Filter your water or boil water when possible. Keep sparge temperature down.