On Sept. 22, Donald Trump pushed an unproven link between Tylenol and an increase in autism in children, and he issued an urgent warning to expectant mothers not to take the medication.

What do we know about the drug? Tylenol is used to treat a several conditions, such as mild to moderate pain, fever, headaches, muscle aches, toothaches, backaches and colds. According to medical experts, when taken as directed, traditional over-the-counter pain relievers like acetaminophen and nonsteroidal anti-inflammatory medicines (NSAIDs) can be safe and effective.

Tylenol wasn't widely used until 1950, when Tylenol Elixir for Children, a prescription medication at first, was promoted as an aspirin substitute, according to Tufts University School of Medicine. Acetaminophen, often sold under the brand name Tylenol, had long been considered the safest option for managing headaches, fever and other pain during pregnancy.