I adopted a cat that was put out on the street by her owner. It happened gradually. First just feeding her outside, then letting her sleep in the house when it was cold. Eventually I got a litter box. I knew who her owner was, but I had never talked with him. I was afraid to go over to his home and discuss adopting the cat. I guess I felt guilty for how far things had gone, and I was also afraid he'd say no. Then I started to obsess that the cat had rabies. I really thought I had contracted rabies. It was my OCD telling me to "take care of business". Talk to the owner, then take the cat to the vet. As soon as I spoke to the owner, who was happy to see her go to a good home, my obsession went away.
Another example is this nose piercing. I am supposed to use cotton balls to soak it in salt water 10 minutes everyday. That is not happening. I even skipped a few days. Then I developed an obsession that I had a life threatening facial infection. It is NOT infected at all. I committed to myself to do the salt water for a few minutes everyday, no matter what. As soon as I did that, the obsession went away.
It is tricky, because I don't want to give the OCD a foothold by giving credence to the obsessions. But, what I find is that while the obsession itself is irrational, there may be something real fueling it. Sometimes my better brain is trying to get my attention. While I need to extinguish the obsession through ERP, I need to try to understand why it popped up in the first place.