I understand your concerns.
These symptoms sound like seveere immune reaction against the spider bite.
Prednisone should help in combating the inflammatory response.
The symptoms should show improvement.
However look for any worsening breathing, persistent high fever and inability to speak signifying asthma exacerbation.
Then he has to go the ER.
Prednisone will not affect Gilbert's which is a benign condition.
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