An expert on car seats revealed why parents and caregivers should never cover their child's car seat or stroller with a blanket or other fabric in the mistaken belief that this can keep a child safe from the sun. 

While it's common knowledge that leaving a child in a hot car on a sunny day can turn deadly very quickly, a car seat or stroller inside or outside a vehicle also can be potentially life-threatening if it's covered by fabric — as a woman on TikTok has demonstrated.

Michelle Pratt, founder of the Tampa, Florida-based organization Safe in the Seat, released a series of TikToks during the month of May showing just how hot a car seat can get in the sun — and how a practice that many people think protects children can actually harm them. 

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Safe in the Seat provides courses, consults and other resources to ensure that parents and caregivers safely install and use car seats for their children. 

"Temperatures are rising and while you may be tempted to completely cover your child to protect them from the sun, you would be doing more harm than good," said Pratt in a May 3 video posted on TikTok. 

"Placing a blanket or cover over the top of the car seat can create a ‘greenhouse effect,’ limiting airflow and causing temperatures to rise to dangerous levels," she revealed.

To demonstrate this in a video, Pratt placed a thermometer in four strollers, each covered by a different type of material, including blankets, a mesh fabric and a built-in parasol.

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After just 10 minutes, the temperatures of the strollers rose from 92 degrees to over 100 degrees. 

After 30 minutes, the temperature in the strollers was well over 100 degrees — deadly temperatures for a little one.

"Bottom line: These types of covers create dangerously high temperatures inside of your car seat," said Pratt. 

She added, "All the more reason that I want you to get your kiddo out of the car seat as soon as possible." 

A parent or caregiver out with a child in a stroller on a sunny day should take "frequent breaks" with their child and "consider adding a fan" to improve air circulation and reduce heat, Pratt noted urgently.

"I know you think adding covers like these is going to protect your child," she said. 

"I hope you learned that it does quite the opposite." 

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Said Amber Rollins, director of Kids and Car Safety, a national nonprofit devoted to preventing injuries and death to children from vehicle-related incidents, to Fox News Digital, "In the summer heat, it is not recommended to cover children with a blanket in their car seat."

The dangers of covering car seats with blankets goes beyond the risk of overheating, said Rollins, who is based in the Kansas City area. 

"Not only can this cause heat to be trapped inside the car seat, but it also is a suffocation hazard for very young children," she said. 

Rollins' tip for parents who want to block babies from the sun while they're in the car is to use proper window sunshades, she told Fox News Digital. 

In her follow-up videos, Pratt tested a car seat canopy cover, offered on many brands of car seats, as well as a muslin blanket that was soaked in water and draped over a stroller.

Pratt found that the temperatures in a car seat fitted a canopy cover increased from 90 degrees to 95 degrees in just five minutes. 

After 30 minutes, the temperature was 107.5 degrees — a level that can cause heatstroke and death in children. 

When Pratt tested a damp muslin blanket over a car seat that had been sitting in the sun, she found that the temperature increased from 113 to 127 degrees.

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"Any time you completely cover your car seat, the temperature inside is going to rise significantly — whether [the cover] is wet or not," she said.