This is the question that decides whether you use parenting tools or OCD tools — and using the wrong set is why nothing has worked.
If it is defiance, consequences and consistency help. If it is OCD, consequences make it worse — pressure feeds the anxiety that feeds the compulsion, and you get an escalating loop plus a child who now feels ashamed.
Externalize it. Name it — the Worry Brain, the Bossy Brain — so it is you and your child against a third thing rather than you against your child.
Reduce accommodation gradually, not abruptly. OCD grows on accommodation, but yanking it away in one day produces a crisis. This is exactly what SPACE (Dr. Eli Lebowitz, Yale) is built to do, and it works entirely through the parent.
And treat the flare underneath. If the OCD tracks the illness, the fastest route through it is lowering the neuroinflammation driving it.
Stop trying to argue them out of it. A flaring brain cannot be reasoned with, and every failed logical argument teaches your child that you do not understand — which makes the next one harder.
Want this answered for your own child? A Plan B synthesis reads every lab and note you have — together — and tells you what is driving the picture, what has never been checked, and what to ask for next.
The first one is free, and you keep the list either way. Phone photos of labs are fine.
Plan B for PANS is written by a parent, not a physician. Nothing here is medical advice or a substitute for your child's clinicians — it is meant to make you the best-informed person in the room when you talk to them.