It's a warning you wouldn't think anyone other than a small child would need, but it turns out toddlers aren't the only ones at risk of picking up and eating detergent pods.

Some parents need to worry about their teens, too, because of a recent and dangerous trend on social media, in which young people film themselves taking the "Tide pod challenge" — putting the pods in their mouths and biting, releasing the liquid inside.

About 40 teens in the U.S. have been treated so far this year after ingesting the liquid detergent in pods, poison control centres say.

The detergent is poisonous, according to the U.S. Consumer Product Safety Commission. Ingestion can cause vomiting. Children who take it into their lungs can suffer from long-term breathing difficulties, health experts say.

Tide's parent company, Procter & Gamble, said in a statement it is "deeply concerned about… intentional and improper use of liquid laundry pacs."

The company has also collaborated with New England Patriots tight end Rob Gronkowski to put the word out, via Tide's Twitter feed, that the pods are only designed to clean clothes.

In the video, the NFL player repeatedly answers "no" to questions about eating the pods.

"What the heck is going on people?" he says. "Use Tide pods for washing, not eating. Do not eat."

What should Tide PODs be used for? DOING LAUNDRY. Nothing else.<br><br>Eating a Tide POD is a BAD IDEA, and we asked our friend <a href="https://twitter.com/RobGronkowski?ref_src=twsrc%5Etfw">@robgronkowski</a> to help explain. <a href="https://t.co/0JnFdhnsWZ">pic.twitter.com/0JnFdhnsWZ</a> —@tide

After the brightly coloured pods were launched in 2012, poison control centres warned parents to keep them away from young children, who might think they're candy.

Media reports said dozens of calls to poison control centres in Canada that year were linked to the detergent pods.

The journal Pediatrics reported in 2016 that thousands of U.S. children younger than six were exposed to either laundry detergent packets or dishwasher detergent in 2013 and 2014, most of them through ingestion.

The detergent in the pods is poisonous. Ingestion can cause diarrhoea, coughing spells and vomiting. (YouTube)

The journal said there were two deaths, both associated with laundry detergent packets.

Health experts say if ingested, the liquid inside the pods can cause diarrhoea, coughing spells and vomiting. Children who aspirate it into their lungs can suffer from long-term breathing difficulties.

The pods also contain a chemical known as 1,4-dioxane, a solvent that can cause eye and nose irritation, and kidney problems.