An apparently gluten-induced photosensitivity in horses.

The researchers observed a severe type of skin inflammation caused by light exposure, known as photosensitization, in three Appaloosa mares, a breed of horse. They suspect the condition was triggered by the horses eating a gluten heavy food. The skin inflammation improved once the horses stopped eating the suspected food and were no longer exposed to sunlight.

Research Context and Objective

• The study was built on the observation of primary photosensitization, a skin condition believed to have been triggered by light exposure, in three Appaloosa mares.
• The key objective of the research was to determine what caused the skin condition and find effective means of treating it.

Observations and Methodology

• The researchers followed the development of the skin condition, which advanced from basic redness (erythema), to swelling (edema), oozing, and eventually to dry gangrene and ulceration.
• They noted that the horses’ diet included a suspected dairy concentrate feed rich in gluten.
• To confirm whether the diet was the cause, they stopped giving the horses the suspected feed and also ensured that the horses were not exposed to sunlight.

Results and Conclusion

• After the changes in the horses’ diet and exposure to sunlight, the researchers noted that the skin condition resolved, indicating the feed was probably the cause.
• In a control experiment, ponies and a donkey that did not eat the suspect concentrate did not display any of the skin conditions observed in the Appaloosa mares.
• This led the researchers to conclude that gluten ingestion and possibly its metabolites could contain photodynamic agents that cause photosensitization in horses, hence the observed skin inflammation.