Tylenol is typically used for minor ailments like headaches without considering repercussions such as overreliance on medication. This can lead to medication immunity or lack of understanding towards the chemicals in medication, which also leads to unwanted drug interactions. 

Pharmacist and digital health educator Ethan Melillo has drawn attention to the ingredients in NyQuil. 

Among the most concerning, he said, is the syrup’s listed 10% alcohol content and the significant dose of acetaminophen. Since alcohol and acetaminophen are processed through the liver, taking them together can increase the production of toxic byproducts that  damage the liver.

Pharmacists, including Dr. Melillo and the Mayo Clinic, have highlighted the severity of the risk. In a Jan. 21 report, the journal Frontiers in Immunology referred to it as an “invisible killer.” The condition is known as drug-induced liver injury.

Pain relievers are the leading cause of Drug Induced Liver injury, or DILI. That category includes acetaminophen as well as nonsteroidal anti-inflammatory drugs, which include ibuprofen, found in Advil and Motrin, and naproxen sodium, found in Aleve. Experts said the danger is not only in the combination of drugs, but also the dosage and how it accumulates over time, sometimes reaching unsafe levels even when patients follow their doctor’s prescription.

NSAIDs and acetaminophen are not the only drugs linked to DILI. Thousands of others carry the same risk including opioids, proton pump inhibitors and diabetes medications. 

Herbs and supplements are a less obvious culprit, accounting for up to 20% of DILI cases. 

Green tea extract, mistletoe and kava are among the supplements linked to liver damage, serving as a reminder that even products marketed as beneficial can cause harm through interactions or excessive usage. 

To combat DILI, scientists and healthcare workers are studying biomarkers to identify genetic factors that make some people more vulnerable to liver damage. 

Five biological subtypes of liver damage have already been identified, though research in that area is ongoing.

While genetic research continues, experts say the simplest solution is to take as few drugs and supplements as possible. According to the drug labels on medications, products should only be used as directed.