CHARLOTTE, N.C. - A Facebook post showing two cats seizing because of flea and tick medication has gone viral, and has pet owners worried.

Local experts say it happens far too often, usually when people use cheap over-the-counter products.

“It's five dollars for a reason,” said Jay Hreiz, a veterinarian at Ebenezer Animal Hospital in Rock Hill.

“Usually, when they're priced really low, it's because the ingredients are not reliable.”

He says many of the cheap drugstore products won’t list all the ingredients. And that can lead to devastating side effects like what was depicted in the videos.

“It’s more common than you think,” Hreiz said. “They're going to be snapping at the air. They're going to be tremoring uncontrollably. Their eyes may be making erratic movements. Sometimes, they can be foaming at the mouth.”

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Hariz says it usually happens with cats, and often when owners mistakenly use products meant only for dogs.

“All the way at the bottom, in very small print, it says ‘not intended for cats,’” Hreiz said. “But people don't read that. We're just going off blind trust.”

He says there are other important things you should look for too.

“Avoid products with permethrin in it. It has direct neurological side effects.”

Side effects that could change your furbaby forever.

“You could have potential brain damage which would alter the mood and the character of your pet potentially permanently,” Hreiz said.

The good news is the animal clinic worker who posted the videos on Facebook says the cats are back to normal and on the mend.