Research have shown that most skin problem occur as a result of defective healing of the burn,piercing of the skin(i.e ear lobe,nose),other causes are shaving against the direction of the hair,family history ( hereditary) any type of skin wound/ puncture can induce the body to overproduce the extra collagen.SOLUTION: when you discover rash/ bumps at the back of your head,best thing is not to touch/ handle at the early stage.avoid piercing,surgery and other form of self medication requiring incision of the skin would/can make the keloid,bumps,wart etc recur even bigger than the initial size.the best solution is to avoid or prevent and if not please contact a specialist.you can also send questions to this mail Deeteebumps@yahoo.com for free consult.