The toxin is gaseous and, if released into the air or inhaled by the body, forced the victim's brain to trigger the fear of their worst phobia. Though the length of the effects could vary, it can be nullified by adrenaline.
After Nora Fries shot Killer Frost with a freeze ray, Barry Allen and Oliver Queen came to help. Oliver tried to use his speed to throw a lightning bolt at Nora, but missed and knocked over a box containing the serum, causing the vials to shatter. Oliver and Barry then started hallucinating, seeing each other as Eobard Thawne and Malcolm Merlyn respectively.
- Hallucination: The serum can cause strong hallucinations that are hard to dispel, as shown when Oliver and Barry didn't realize they were fighting each other until Batwoman knocked them out.
Behind the scenes
- In the main DC Comics continuity, The Scarecrow's Fear Toxin is the toxin used by the Scarecrow to commit his crimes praying on people's fears.