Fireworks, traditionally a part of Fourth of July celebrations, can trigger frightening reactions in veterans suffering from post-traumatic stress disorder, mental health experts say.
The explosive noises that accompany many types of fireworks can affect veterans with PTSD, causing flashbacks to traumatic combat experiences involving gunfire and explosions, they say.
"This is something that every veteran and clinician knows about but the general public doesn't know about this," says Dr. Deborah Beidel, a psychology professor at the University of Central Florida in Orlando.
Around three-quarters of veterans diagnosed with PTSD report loud noises, and fireworks in particular, are difficult to deal with.
"Veterans tell me that they sit in house with TV as loud as they can make it and drink as much as they can to get away from the [firework] sounds as much as they can," Beidel says.
One nonprofit group, Military with PTSD, has launched a campaign to educate the public about the effects fireworks can have on combat veterans.
Shawn Gourley, whose husband Justin is one of around 500,000 veterans of the Iraq and Afghanistan wars diagnosed with post-traumatic stress disorder, started the group on Facebook.
This year, Shawn says, the group has launched a program of providing free lawn signs saying "Combat veteran lives here, please be courteous with fireworks," to veterans and their families who've requested them.
The group has mailed out almost 4,000 signs, she says.
The group says it wants residents planning on celebrating the holiday with fireworks let their military veteran neighbors know when and where they plan to do so.
"All they want is a heads-up," Gourley says.
Other veterans with PTSD have talked about what the noise of fireworks can do.
"You hear that boom, it can trigger you right back to something -- a place you don't want to go," says Iraq war vet Eric Calley in Lansing, Mich.
Calley has a therapy dog helping him cope with PTSD, but the Fourth of July is a particular challenge, he says, and can make him feel he's right back in a war zone.
"It's almost like tunnel vision, nothing on the outside of you even matters," he says.
While PTSD can affect anyone who's experienced a traumatic or life-threatening event, the risk of developing the condition is especially high for combat veterans, medical experts say.
More than 30 percent of Vietnam War veterans have had issues with PTSD at some point, the U.S. Department of Veterans Affairs estimates, as have between 10 percent to 20 percent of people who served during the first Gulf War of the wars in Iraq and Afghanistan.