Hi,my 11 Yr Old Daughter Has Had A Reoccurring Infection

hi,my 11 yr old daughter has had a reoccurring infection on her thumb under her skin.She has been to the Dr.several times and treated with various anti biotic and anti fungal medications but it keeps returning? It started in 2010 the 1st time and within 2days her thumb was black and blue. Each time it starts the same..little white dots under the skin..the fatty pad part of her right thumb every time tho I have been told by the dr's none of the incidents have any connection to the next? There is never any opening in her skin..the white dots appear and multiply and her thumb is hot to the touch and painful to the touch. If not noticed and treated soon after it seems to escalate quickly. Last time she had a red streak going up the inside of her arm to her elbow area by day 3. It again appears to have started in the same exact area..this will be the 6th time since 2010. At the last er visit they took x-rays and did blood work and lanced her thumb and found nothing? Any ideas what could be causing this?