Reddit users have joked about "natural selection" for shoppers after Tide Pods were spotted stocked on shelves at the end of a supermarket snack aisle.

The juxtaposition was spotted in a US Walmart at the height of the Tide Pod Challenge in January. It is unclear where the branch of the supermarket is located, but it came as more stores have been spotted locking up their Tide Pods to deter thieves.

Charles Crowson, senior manager of corporate communications for Walmart, said: "No retailer is immune to the challenge of crime and Walmart is not exempt. The decision about which items are subject to additional in-store security is made on a store-by-store basis at the discretion of the store manager." Crowson told IBTimes UK that the decision to place detergents under higher security measures is not connected to the viral challenge, despite rumours.

In the first four weeks of 2018, 131 teenagers were treated by US poison control centres after intentionally exposing themselves to single-use laundry detergent, with the rate continually rising from just 39 cases in the first two weeks of the year.

The American Association of Poison Control Centers (AAPCC) data showed that the same centres handled 39 and 53 cases of the same age group across an entire year in 2016 and 2017 respectively.

The Tide Pod Challenge involves biting into one of the laundry packages, which is filled with chemicals, while on camera, before posting the video on social media. The AAPCC has released a "high alert" warning about the trend, saying the potential effects include seizures, pulmonary edema, respiratory arrest, coma and even death.

Reddit users joked that the image of Tide Pods right by the snack aisle was a classic case of natural selection and that it was "true capitalism" just giving people what they wanted.

There was a mixed reaction overall, as one user described it as "mildly concerning" and another counteracted by saying Walmart had been "opportunist, creative and funny," giving them three thumbs up.

AAPCC has issued a general advice to anyone who eats a Tide Pod in the US urging them to immediately contact the national Poison Help hotline on 1-800-222-1222, where experts are available round the clock.