Interesting! The drug is almost working homeopathically. The toxic reactions of the drug (which signal it's homeopathic indications) are about Yang rising, creating buphthalmos, glaucoma, seizures etc. If the drug is not being used, then symptoms of Yang rising are possibly appearing.
To test the theory, try Chai Hu Jia Long Gu Mu Li Tang (Bupleurum, Dragon Bone and Oyster Shell Combination), which I do use in allergic dogs, especially if the lesions are on the head and around the eyes. Be ready as well with Bu Zhong Yi Qi Tang (Ginseng and Astragalus), in case the CHJLGMLT somehow aggravates the symptoms. The latter will work if the former does not.
If you don't have those formulas on hand, then the owner can source their equivalents OTC from Gold Standard (www.goldstandardherbs.com). The CHJLGMLT is contained within Halscion. The BZYQT is contained within Galvanex.
Let us know how things go as this is a unique little case you have there!
Steve