When she gets the lumps, is there any sign, if you can examine the skin, of an insect bite, maybe a spider bet that is getting infected? I've had a mosquito bite do a similar things a couple times in my life, as I have very sensitive skin and it doesn't take much. And when it gets infected, of course, one's whole immune system kicks in ...

In what part of the country do you live? Different critters in different places ...