"If the food is totally unprotected; if the workers are without hot water or the ability to go the bathroom when they need to use the restroom; that's another good indicator," said Angelo Bellomo, director of environmental health, L.A. County Dept. of Public Health.
You'll find illegal food vendors on streets all over Southern California. A video of a raid shows where authorities found more than a dozen illegal food carts.
"There'll be cut fruits here, but the food is not stored properly," said Bellomo. "And the preparations that will be placed on the food are not protected from the elements."
They pop up everywhere, even in front of schools selling to kids.
"They're not supposed to be selling food to the kids," said Miguel Verdusco, an L.A. resident. "You could be poisoning the kids. I don't know what they give them. How are they making the food? I don't know. They're washing their hands? I don't know."
Those bacon-wrapped hot dogs don't look quite as good once you see how they're stored.
"It's just a cardboard box. It could have been contaminated before the food was actually placed in the box," said Bellomo. "But then again, there's the potential for the food to be contaminated just by virtue of the fact that the top is open, and it being traveling to the location. And of course the box is not refrigerated."
Health experts say it's not just the fact that vendors don't have permits; it's that you have no idea where they're getting their food from. They say the potential of getting sick from it is higher because it can be contaminated anywhere along the way from the source to the cart.
To give you an idea of what you might be eating: Officials say sometimes there's no place to prepare the food except a public restroom -- the only place that has running water. And sometimes it's a gas station bathroom.
So what are authorities doing about it? LAPD officials said they're trying to raise awareness in the community, but because the vendors can move around easily, it's hard to pin them down.
But if you see a vendor you think may not have a permit, there is something you can do.
First of all, look for stickers that say they are licensed. If they're not, it may not be safe to eat there.
You can also call the L.A. County Health Department, but be persistent if you want results. Keep this in mind: There are only 10 inspectors for the entire county of Los Angeles.
When one vendor was asked about a license, he admitted he didn't have a permit to sell prepared food. He doesn't pay taxes, and inspectors never check his food. The Department of Health estimates there are 15,000 vendors out there just like him.
A few minutes after Eyewitness News asked questions, he left, only to set up somewhere else.
"These are frightening and startling situations that exist here," said LAPD Senior Lead Officer Martin Martinez. "You feel for the fact that they're trying to make ends meet. However, they're putting the general public in harm's way."
Remember: There are inherently more dangers in a cart or truck serving food than a restaurant simply because of space limitations. That means refrigerators may not cool food sufficiently and there's a greater chance food may be left out too long.
Look for a license, and if in doubt, keep walking. It's not worth the risk.