Based on the context and the answer, generate a question. 

Context: My right arm has been starting to worry me . It has recently begun to have a strange sensation in on of my veins . It feels as though my blood has turned into a thick substance with a million ants in it . When my arm points up , I can feel my blood & what seems to be ants rushing slowly down my arm .

Answer:

They feel a strange sensation .



Why is the narrator worried about their arm ?