Makeup is a fun and inexpensive way to create a look. Many kids use face paints because they're not allowed to wear masks to school.
The nonprofit Ecology Center warns parents to beware. It tested 31 types of makeup from big box stores and found half of them contained cadmium, which is a naturally occurring metal that can be unsafe at certain levels, depending on how humans are exposed.
"If people are putting it topically on their face for makeup, it should be a smaller reaction, but it's always a possibility," said dermatologist Thomas Su.
Su said if there is cadmium in some costume makeup, he's never seen any negative effects. But he added that parents should be more careful with makeup if their kids have acne or scratches on their faces.
"If their skin is nice and intact, then the chances are pretty low that you'll get enough absorption into your skin that will do too much damage," said Su.
Some pediatric experts said face paint is actually safer than wearing a mask, because a mask can obscure vision.
Even though masks are a big part of Halloween sales at The Costume Shop in Glendale, owner Tim Dietlein said parents should take the masks off their kids at night.
There are other things parents can do to make sure trick-or-treaters stay safe. Reflective tape can help make sure everyone sees them when it gets dark.
Check the costume length to make sure kids don't trip. And avoid those special "one use" contact lenses. They can irritate eyes because they're not properly fitted.