My child has had bumps on arms and legs and bottom for 4 years now (he is 8). They are usually filled with a hard core if squeezed, but sometimes they can be very inflamed and filled with pus. The bumps have spread now to his back and stomach. He has been to several doctors, and not one has been successful in helping to clear these bumps. My son tells me that they can sometimes be very painful when inflamed, especially the ones on his bottom. What could be causing this? food allergy? something else? please help. He has also been taking zoloft for OCD behaviors since 4 years old, could this be a side effect? Was told that this doesnt really fit the diagnosis of KP.