Nettle agents or urticants are a variety of chemical warfare agent that produces corrosive skin and tissue injury upon contact, resulting in erythema, urticaria, intense itching, and a hive-like rash.
Most nettle agents, such as the best known and studied nettle agent, phosgene oxime, are often grouped with the vesicant (blister agent) chemical agents. However, because nettle agents do not cause blisters, they are not true vesicants.
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Nettle agent Wikipedia(Text) CC BY-SA