My DD recently had a very sore, very swollen arm and hand. Only the left arm, the other limbs were all fine.
She was whipped into hospital for 2 days of intravenous antibiotics, followed by a week's course of antibiotic tablets at home. The arm got better.
At the GPs, after that, she was told that her blood tests, taken at the hospital, were all clear - no infections, so no apparent reason for the swelling.
Does anyone have any idea what could cause an arm and hand to swell like that?