Hello. I would like to help you find an answer.
This could be a sign of dehydration along with an abdominal infection or a kidney problem like a stone or infection
It could be serious. It's hard to tell without any other information.
I think you need to have this looked at.
Xrays of the belly
Go to urgent care. It will be faster and cheaper than the ER.
If you have follow up questions, please ask prior to accepting.
I doubt its the anti histamine.
Another possibility is something called IgA nephropathy or Berger's disease.
This is inflammation of the kidney after a viral infection.
If you are taking claritin, I'm assuming you are having symptoms of a possible viral infection.