I'm Dr. Jo and I'm here to help you with your question about the swelling on your dog's paw. I'm so sorry he isn't doing well, but glad you're looking for the information you need.
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Please let me begin by saying it's hard for me to understand what you mean when you say it's the sweat gland in his paw that's swollen. Dogs don't have sweat glands in their paws to speak of, so I wonder what you're seeing.
There are a lot of other things that can cause a paw to swell, most commonly stings and puncture wounds and penetrating foreign bodies like thorns and grass seeds. These can cause the whole paw to swell up red and puffy, or make a large, puffy red blister between the toes.
Another thing that could look like a swollen sweat gland on a paw would be any of a variety of skin tumors
If you'd like to click on the paperclip icon to upload a photo of your dog's foot, I'd be happy to take a look.