Allergent was a man named Maxwell Veezey. He suffered from severe allergies, of which medications had little effect. Hoping to escape from all plant life, he moved to Gotham City. After finding that Gotham City had plenty of trees and plants, he donned a toxin suit and spread herbicides and defoliants throughout the city parks. When Poison Ivy learned of this, she broke out of Arkham and tracked him down. Before giving Allergent a lethal kiss, Batman interrupted them. After a brief fight, Batman managed to subdue Ivy. Allergent managed to get away but he was soon captured by Lock-Up, a vigilante villain who believed criminals should be given harsh sentences. Batman, Robin and Nightwing later rescued Veezey and the other inmates from Lock-Up's prison. Allergent has not been in any other appearances so far since then.