This happened with Shyla when she was younger. I went to let her in a noticed that she had lumps all over her head and ears. In fact, her ears looked like there were blown up with air. They we so puffy. I gave her half a benadryl right away and another half a little later. I took her to the vet the next morning and they were almost all gone. He thinks she got bit by some sort of insect when she was outside. Her lumps were about the size of a dime. Horrible and very scary. This is why I always keep benadryl on hand!!