Hello, I'm Dr. Deb and will do my best to help you today.
It sounds as if Aries may be having an anaphylactic reaction to something...possibly an insect sting or spider bite.
Regardless, antihistamines are the drugs of choice in these situations. I typically suggest Diphenhydramine at a dose of 1 mg per pound of body weight; however, I don't know why Cetrine (Cetirizine) wouldn't be as effective.
The dose would be 5-10 mg per dog up to a maximum of 20 mg if the patient is a giant breed dog (such as Mastiff or Newfoundland, etc). I'd probably give an average 70 lb lab 10 mg. It can be given twice a day if the lumps haven't completely resolved in 12 hours.
Like most all antihistamines, sedation might be seen as a side effect.
Most patients will respond to antihistamines although a few will require steroids before resolution of the bumps.
I hope this helps. Deb
I'm just following up on Aries. How are things going with him and his skin? Deb