My grandson was born with an oval like mark, slightly raised on his arm. - just above his elbow. It occasionally swells in the center like a blister and will burst with clear fluid. It itches him from time to time. The outside is slightly raised and appears almost waxy due to being very tightly raised. What could this be. The dermotologist seemed unconcerned and indicated it could disappear with time. He is three now and other than not having the reaction like a blister as often it is the same.