Since this is an international site, I'm not sure where you are from. How is the mental health care where you live? There is something pretty effective for this called Exposure Therapy or ERP. It's uncomfortable why you do it but works for a good many people. Certainly, not everyone, but for a lot. It's exactly what it says. You are exposed to your obsession. You don't do your compulsions (the washing), you basically put yourself in what your worst nightmare is. An by doing so, it becomes less horrifying, frightening. Desensitizes you to it. ONLY specialized therapists are good at this type of therapy so would search it out specifically if you are so inclined. There are books to try on your own or online guidance (even perhaps online therapy). https://iocdf.org/expert-opinions/expert-opinion-self-directed-erp/ Also, medication along with this can perhaps be helpful with an ocd diagnosis.
OCD is OCD. If it's not necessary and it really is OCD, which we don't know from your post has been diagnosed, it's treated the same as OCD would be in anybody and the blood disease is irrelevant.