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Chromodacryorrhea ("red tears") in a rat. Note typical encrustations around the eyes due to release of porphyrins from the Harderian lacrimal glands. "Red tears" frequently indicates that the animal has been subjected to some form of stress (eg, chronic respiratory disease, changes in environment, etc). These porphyrins will fluoresce pink under ultraviolet light.
Courtesy of Dr. Dean H. Percy.