I own two small dogs. One is a pug, female, 3 years old. The other is a pomeranian, male, 6 years old.
If I put a shirt, or take a shirt off(and this includes harnesses) on the pug while the pom is around, she becomes agitated and starts to growl. Occasionally, maybe three out of the five times she is dressed, she will lunge at him and violently attack biting at his face. We've learned just not to dress/undress her around him.
I'm curious to know why this is happening? She tends to be a little shy around other animals, but she is always fine with my pom.