Six years after the “Benadryl challenge” first appeared on TikTok, doctors are once again warning parents and teens about the deadly phenomenon re-emerging on social media.

The challenge provokes people to purposely take too much Benadryl and fight the drowsy side effects that come with it, which will produce a high.

Benadryl contains the active ingredient diphenhydramine, which is an antihistamine. When used properly, the drug is meant to relieve symptoms of seasonal or situational allergies or the common cold, such as a runny nose or sneezing.

Consuming too much Benadryl also has a lot of medical side effects, such as high heart rate, urinary retention that can cause kidney dysfunction, and arrhythmia, or an irregular heartbeat.

One case saw a 14-year-old female who had a seizure after participating in the Benadryl challenge.

Dr. Stephanie Felton, associate medical director for the Cook Children’s emergency department in Texas, told the Fort Worth Star-Telegram that the hospital saw one recent death in connection to the deadly challenge.

The emergency department has also treated more than 100 patients in the last six months for Benadryl overdose, according to the health system.

However, Felton said that they aren’t seeing as many overdoses as they did in 2020, when the trend first emerged — but the resurgence, which is primarily affecting teens and pre-teens, is concerning.

In 2020, the trend was such an issue that the FDA issued a warning about the dangers of taking high doses of the allergy medicine, which is widely available over-the-counter without a prescription.

The Food and Drug Administration warned that taking high doses of Benadryl can lead to heart problems, seizures, coma or even death.

“We are aware of news reports of teenagers ending up in emergency rooms or dying after participating in the ‘Benadryl Challenge’ encouraged in videos posted on the social media application TikTok,” the agency said in a notice at the time.

“We are investigating these reports and conducting a review to determine if additional cases have been reported. We will update the public once we have completed our review or have more information to share.”

“We also contacted TikTok and strongly urged them to remove the videos from their platform and to be vigilant to remove additional videos that may be posted.”

The FDA advised parents to keep Benadryl at home out of reach and out of sight of children, and lock up any medications that could be at risk of misuse. They also warned healthcare workers to be aware of the trend.

Felton encouraged parents to have direct and honest conversations with their children about social media use and messaging they may be seeing online.

“A simple conversation and continued conversations…are important so we have an open door policy with our kids so that they know that they have a safe place to come to with these questions,” she said.