My chihuahua has been acting very strange.

Question
I have a ten year old male chihuahua. Recently he had an assist on his eyelid. We took him to the vet and they gave him a shot to make it go away. This isn't the first time he has had the shot. A day or two later after receiving the shot he started acting very strange. He is constantly shaking way more than usual. He starting to sit hunched back all the time. He usually loves to go underneath blankets, but now he won't go under them at all. He frequently looks like he is about to puke , but then holds it in. He just seems like he doesn't have as much excitement and life in him like he normally does.

Answer
I am guessing you meant a cyst? I don't know what the injection was but if it was a cortisone injection that could make him feel a bit off for a while.

The injection and his acting strange might not even be related since he didn't react for a few days.
He sounds like he is in pain, either his back or somewhere else. Sitting hunched is an outward manifestation of pain in animals.So is shaking in these little dogs.

You need to call the vet tomorrow and tell them how he is acting since the injection and then bring him in. They need to see what is going on with him since it might not be from the shot at all.

Do not give him any human pain relievers as they are deadly to dogs.
Call the vet in the morning first thing.

I hope he feels better soon.
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Just wanted to be sure of what you were referring to. An assist in my book is a hockey term as I am a hockey fan!