[anonymously]

It is a medicine prescribed for dogs that are suffering with environmental allergies.
http://www.2ndchance.info/Apoquel.htm
“Apoquel, a Zoetis product, is a medication designed to interrupt the inflammatory process that occurs in the skin of most dogs with allergies (blocks or inhibits the pro-inflammatory cascade)”.

I declined it for my dog and chose instead to go to a Board Certified Veterinary Dermatologist, had IDT (intradermal testing) identified the allergens within an hour of the first appointment and started Allergen Specific Immunotherapy, with positive results for over 4 years now.
There is no cure for allergies, it is a lifelong treatment, with stable periods and occasional flareups. Fortunately there are effective treatments available. Allergen Specific Immunotherapy is the most natural way to treat environmental allergies, it is not a medication…..

However, until the dogs condition is stable the veterinarian will prescribe a variety of medications to stop the suffering until the ASIT kicks in (if the dog is started on this) or certain times of the year to control seasonal allergies. And during occasional flare-ups meds may be needed. The meds are helpful and often necessary short-term. I have heard of side effects when they are used long-term. It would be best to discuss these issues with the veterinarian that is treating the dog.