What Could Cause Recurring Pus-filled Lesions On My Uncle’s Arm For 12 Years Despite Repeated Treatment?

Hello, my uncle have something like an infecrtion or something in his arm. It looks like he was bit by 200 ands and each one got a pus sack. Hes been like this for 12 years. When this comes up he goes to emergency and they scrape the whole arm skin. But it comes back again in a couple months. I got a picture