Doctors are sending an urgent warning to parents and teens over the rise of the deadly 'Benadryl challenge' that is re-emerging on social media. 

Making its way around social media sites such as TikTok, the trend first surfaced in 2020 and dares people to intentionally take too much of the over-the-counter allergy drug and then fight the drowsy side effects it causes.

This resistance produces a high.  

However, taking too much diphenhydramine hydrochloride, the active ingredient commonly referred to as the brand name Benadryl, can lead to a high heart rate, urinary retention that can cause kidney dysfunction and an arrhythmia, or irregular heartbeat. 

In 2020, the trend became such a concern that the FDA issued a warning about the dangers of taking high doses of diphenhydramine hydrochloride, which is widely available without a prescription at convenience stores. It is sold under a variety of brand and generic names in multiple types of medication. 

Dr Stephanie Felton, associate medical director for Cook Children’s Medical Center emergency department in Texas, said the hospital has recorded one recent death in connection to the challenge.

The emergency department has also treated more than 100 patients in the last six months for diphenhydramine hydrochloride overdoses. 

Felton told the Fort Worth Star-Telegram that it isn't seeing as many overdoses as it did when the trend first took over in 2020, but the rise, primarily among teens and pre-teens is concerning. 

The FDA warned that taking high doses of the drug can lead to heart problems, seizures, coma or death. 

Diphenhydramine hydrochloride - an antihistamine - is used to temporarily relieve symptoms, such as a runny nose and sneezing, due to seasonal or situational allergies or the common cold. 

A notice from the agency at the time said: '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.

'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 agency advised parents to store diphenhydramine hydrochloride out of sight and reach of children and even to lock up medications that may be at risk of misuse by kids and teens. 

The notice also advised healthcare workers to be aware of the trend and alert caregivers about it.

When the trend first emerged, Benadryl's parent company at the time Johnson & Johnson called it 'extremely concerning and dangerous' and warned consumers to stop participating immediately.

It added that abuse or misuse of its products can lead to dangerous side effects with long-lasting consequences.

Benadryl is now owned by Kenvue Inc. Daily Mail has reached out for comment. 

TikTok has removed any videos related to the challenge from the social media platform and when users search for 'Benadryl challenge,' they are met with the following message: 'Be informed and aware. Some substances can be dangerous when used or misused. Learn more about how drugs, alcohol and tobacco can affect your mind, body and behavior.'

A 'learn more' link then takes people to a substance use and emergency resource page. 

A TikTok spokesperson also told Daily Mail the site's community guidelines clearly state that it does not allow content that shows or promotes dangerous activities or challenges.