I have added human oral Aloe Vera Gel to their daily food.
Page 467 of the Veterinary Herbal Medicine, By Susan G. Wynn, Barbara Fougère
Talks about Aloe Vera Gel internal and external for allergies, etc…
Veterinary herbal medicine - Google Books
Here’s a good article as well:
Household Plants That Heal Your Pet
More info I found:
This book says for tiny dogs give 2 teaspoons daily ??
Page 33
The Natural Remedy Book For Dogs And ... - Google Books
Page 78 – 79
Natural Remedies for Dogs and Cats - Google Books