CRP could definitely go up with any illness. It does tend to go up and down much faster than ESR. For what it's worth, my daughter's doctors all say that CRP is more useful than ESR - they rarely check her ESR now, but do follow her CRP and of course, Fecal Calprotectin.
This is an extreme example but a couple of weeks ago, my daughter was hospitalized because her blood work was all over the place - her liver labs were very elevated, her WBC was elevated and her CRP was hugely elevated.
In the course of 6 days, her CRP went from roughly 130 (!!!!!!) to 60 to 20 some to 11 (range was 0-3). Her WBC went from high to normal and a serious infection was ruled out. ESR was 44 at its lowest (range was 0-20). She asked both her rheumatologist and GI why her CRP was so high and they both said they honestly did not know and it's possible she had a virus, but also that we may never know. Her arthritis is severe and hard to control so her CRP has been high for 5 years now - it only comes down on steroids.
CRP should not go up with a steroid, especially a foam. My guess is just that Humira hasn't fully controlled the disease.
I can't remember - have they done Humira levels? And/or antibodies to Humira?