Lewisite diagnosis

Phenyldichlorarsine, ethyldichloroarsine, and methyl-dichloroarsine have similar properties and toxicities as lewisite. They may be mixed with sulfur mustard similarly as can be done with lewisite and mustard mixtures, and this can confuse the diagnosis between either an arsenical or a mustard injury. 

Lewisite Vesicant Exposure Clinical Presentation and Diagnosis... 

The differential diagnosis of mustard casualties on the battlefield after a known chemical attack is not difficult. The history of a chemical attack is useful, particularly if the chemical agent is known. Simply questioning the casualty about when the pain started, whether it started immediately after the exposure or hours later, is very helpful. Pain from Lewisite (the other vesicant that causes blistering) begins seconds to minutes after exposure pain from mustard does not begin until the lesion begins to develop hours later. 

F. H. Adler and I. H. Leopold, Symptomology and diagnosis of Lewisite ocular lesions, Faciculus on Chemical Warfare Medicine. Vol 1-The Eye, National Research Council, Washington DC, 1945, pp. 289-295. 

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