Effects - Why no more numbness?

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When SWIM started doing coke his nose, mouth, lips, throat, and all arround his nose in his face would get all numb. 3-4months passed and SWIM just started not to get numb at all. SWIM then was doing it very heavily for 5-6months, and stopped for arround 6months. Now SWIM started again thinking he would get that numbing feeling back, but none, swim barely gets any numbness, no mater how much he puts in his mouth or rubs on to gums. Little to no numbing. SWIM is not concerned about the product's quality becuase he knows its very good. SWIM has other friends who do the exact thing and they go completely numb. SWIM has also done other peoples things in different cities too, and didnt get numb....

Is something wrong with SWIM? Or is it common that you can't get numbness back anymore?