My senior Shih Tzu has severe skin issues. Could it be autoimmune?
I would also suspect an autoimmune disease like systemic lupus erythematosis with what you are describing. These are terrible diseases that are often difficult to treat. It appears that Roxy's current treatment is not very effective, so I would recommend scheduling a recheck exam with your vet. There are stronger medications that can be given.
I would also want to ensure the disease is accurately diagnosed. This usually requires that a skin biopsy be done and sent to the laboratory for analysis. If this has not been done, then I would ask your vet about it. It's not unheard of for a case to be treated for autoimmune disease when the actual diagnosis was something different (i.e. skin cancer, mite infestation), so it's important to have a biopsy and histopathology (lab analysis) done.
For more information about the suspected condition and autoimmune diseases, I recommend you read the short articles at the links below.
https://vcahospitals.com/know-your-pet/systemic-lupus-erythematosis-sle-in-dogs
https://vcahospitals.com/know-your-pet/autoimmune-skin-disease-in-dogs
I hope that helps and poor Roxy gets better soon.
Updated on September 23rd, 2025