“What the difference between the two is that ibuprofen has more of an anti-inflammatory effect. It effects the cells that mount an inflammatory response and more efficiently than acetaminophen,” Dr. Klein said. “So our body’s defense mechanism, which help us fight off infections, are also what cause our fevers. Ibuprofen is a little better at controlling that. The speculation is that we are limiting our defense mechanism by taking ibuprofen in ways that we won’t by taking acetaminophen.”