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Vet School Team Solves Dog's Mystery Rash


Other options for reducing contact with the plant include booties and/or a body suit. Unfortunately, Max is too large for a body suit to be effective, as it leaves exposed the very areas that need protecting. Another way to mitigate the rash is to rinse or thoroughly wipe down the dog after every potential exposure. By also using shampoos such as Malaseb, alone or mixed with a bit of Selsun Blue, the chance of secondary staph and yeast infections can be reduced.

Studies have shown that dogs build sensitivity over time but may not show a reaction until as late as two years old. And once started, it tends to get worse, according to the research. “Every time the dog comes in contact with the substance, the reaction is likely to worsen,” wrote Gail Kunkle, DVM, in a paper about canine allergies presented at a 2000 Dog Owners and Breeders Symposium at University of Florida College of Veterinary Medicine. “There are steroids which are used in severe cases to relieve the inflammation but these are not good long term solutions,” she wrote. “The most difficult part of managing a contact allergy is that it [requires] a lifetime commitment from the owners, as it is unlikely the dog will ‘outgrow’ the reaction or improve over time. Some owners have resorted to making concrete or rock kennels in their yards or even using Astroturf if the problem is a grass or weed. The common plants that cause this reactivity in the dog are very difficult to eliminate from your yard and, in some cases, clients have literally killed the grass and the weed has thrived.”

We have chosen to eradicate this otherwise wonderful plant on nearly an acre around our house, and we are considering a fence to keep Max from roaming on the rest of the acreage, where we are unable to tame this native menace. Botanical sources indicate there are 350 species in the Commelinaceae family, and all contain calcium oxalates. Some species are so tiny (e.g., Murdannia spp.) that they look like grass until you get on your hands and knees to see their minuscule purple flowers! Other plants, such as taro (Colocasia esculenta), also contain calcium oxalates, which should not be confused with plants that contain oxalic acid, such as spinach or sorrel.

Max is only outside when we are, so we can keep an eye on him. But still, he occasionally experiences a thrilling moment when a deer wanders by and taunts him into a good run, which the deer invariably wins. On his return, after successfully evicting an “intruder” from our property, Max gets a sudsy rinse on his underside, just in case.

Dr. Marsella told us that Commelinaceae allergy is a greatly underdiagnosed condition in dogs. She hopes that more exposure to the issue will encourage veterinary clinicians to consider it as a cause of chronic rashes and infections. We can vouch for the fact that the patch test is simple, painless, and conclusive. We are grateful to the students and faculty at the UF College of Veterinary Medicine for improving Max’s quality of life.




Eleanor K. Sommer is a freelance editor and writer with a background in the traditional use of herbs.

Photo of Sam the dog by Günter Hentschel

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