Sometimes after i shoot meth my arm gos red,very warm to hot to touch and I get welts like sand fly bites( 5 cent piece size) around injection site. All symptoms last up to 20 mins. I no its not from a miss ,I use clean needles n swab iv site. I could have a hlf g bag and only i use out of it and one shot won t do it and then the next shot from same bag will do it. It happens from same or different batches of meth. What causes this???? Is it ph levels or epsom salt or msn used to cut the meth