The hot burning embers can damage the cornea, which is the clear part on the very front of the eye. It's a key component of vision because it reflects light on to the retina.
When the cornea gets scratched or damaged, it can be blinding, and sometimes the damage is permanent.
When Jannette Hernandez's young daughter was twirling a sparkler around, no one expected her to get burned.
"She was waving it around, and it actually hit her stomach, and it went through her shirt, and she got a little scar on her stomach," Hernandez said.
It's a scar you can still see seven years later. So what if it hit her eye??
"As an eye surgeon, being on call on the Fourth of July can be a really heart-wrenching experience," said Dr. David Richardson, an ophthalmologist. "These sparks can just fly into the eye, and if they hit the cornea, that can actually cause permanent visual loss."
According to the 2011 fireworks report, in the one-month period surrounding July 4th, officials recorded 6,200 injuries, and 1,100 were eye injuries. Sparklers accounted for the largest number of injuries to children under 5.
"We can expect that about 500 people this year are going to permanently lose vision from fireworks," Richardson said.
If a child gets an eye injury from a sparkler, do not rub or touch the eye. Get them to an emergency room so an eye surgeon can examine the injury. Some injuries don't look bad, but they can be dangerous and blinding.
"We're really discovering that there are no safe fireworks that you can use as an individual," Richardson said.
Richardson notes sparklers are sold in multiple packets, so it's possible parents will end up with more than they bargained for. His advice: Don't buy them at all.
Sparklers burn at temperatures of about 2,000 degrees - hot enough to melt some metals. Even when adults use fireworks, the American Academy of Ophthalmology recommends using goggles.