weird skin thing

hi im a 25yo male
i have this weird skin thing every time i get scratched on my legs, it get really infected or something
been to doctor may times, they give me anti biotics and eventually goes, but not after lots and lots of pain
get yellow dots on it and they ozze out filth.

basically it keeps coming back everytime i get a scratched. or cut even is it only draws lil bit of blood.

first time i memba it was prob few years ago now, i fell over at a concert and grazed my elbow, then it was scabbed over and i went to a botanic garden, all different types of bushes and trees, and elbow brushed on one, then few hours later i was in excruciating pain, felt like a really bad spider bite or something, but ever since then it keeps coming back, could it be some kind of poison ivy thing.

also i'm fairly tattooed and ppl reckon its cos i'm having reaction to the ink, but i fine until i get a scratch or cut on arms or legs, mostly legs.

please help this is really weird, and i hope not somethng major. thanks

p.s im vegetarian