Sound that make skin feel hot and cold

Alexander was sitting outdoor and doing his home work while his sister is practicing her swimming with her team. I helped him to move the plastic folder and his home work over to other side of table. Alexander covered his ears and shouting: “Mom, you make the sound make my skin feels hot & cold!!!” I could not believe how this minor scratch sound would do that, so I did again to see how he does. He really shaking his body and told me again, “Mom, stop it! You make my skin feel hot and cold again!!!” I looked at him and amazed by how sensitive he is. I felt so sorry and would not do it again.