For a person with trauma in her or his past, whether the trauma be military combat, having suffered child abuse or anything else, a trigger is something that reminds them so much of the past trauma that they leave here/now and go to there/then. What gets triggered could be an actual flashback (reliving, as though it were now, some previous traumatic event) or the feelings associated with some previous traumatic event.
Anything can be a trigger. Triggers can be objects, actions, words, smells and attitudes. If you or someone you are with seems to be reacting inappropriately or out of proportion to a situation, it could be the result of a trigger. TV shows and movies can be sources for very potent triggers - one will often see people running out of theatres during graphic rape or combat scenes.
Someone with PTSD (Post Traumatic Stress Disorder) who is triggered by something will often experience either an anxiety/panic attack or a dissociative fugue. It's not unheard of for people having anxiety/panic attacks in these situations to do something unsafe without realising it, like running out into the street after being startled by someone. Even without causing actual physical harm to the individual, these incidents can be personally embarrassing and interfere with functioning at work and/or school.
When dealing with a trigger, the first step in returning to here/now is to get focused on something that is clearly here/now and not there/then. That 'something' could be Christmas decorations, the apartment building across the street, current popular music on the radio or anything else that can bring the person back to the present.
It is probably a good idea for a person who has just 'got back' from such an experience to examine what caused it and why, to avoid that trigger in the future or to avoid being affected as badly by the same thing in the future.
Once a person, and anybody closely associated with that person, knows his/her triggers, they are easier to avoid. When a person knows how to identify that s/he is triggered, it's not as difficult to get back to here/now. For that reason, if no other, knowing how to identify a trigger and tell when a person has been triggered is important for the person to whom this happens and anyone who cares about that person.
Post Traumatic Stress is not something you have to live with forever. For a discussion on possible treatments, visit the National Center for PTSD
If you're living with Post Traumatic Stress now, here are a few links to online support groups:
PTSD Sanctuary is an educational site and research resource for people working in the mental health field, as well as people with PTSD and their families.
About.com Trauma and PTSD Resources Listing has links to over 20 related Internet sites.
About.com Panic/Anxiety Disorder Resources Listing has a number of links to PTSD related sites.
PTSD.com contains a comprehensive listing of online resources for people with PTSD and their loved ones, including newsgroups, chat rooms, discussion boards, email groups, newsletters and much more.