What Causes Spider Veins On Upper Chest And Arms?

I have what looks like spider veins on my upper chest and on my arms. I have had this since I was a young child and I will be 40 this year. My doctor thought it may be HTT but I do not have any of the other symptoms, ie bleeding, liver problems, etc. This rash (or whatever it may be) becomes a brighter (more red) with nervousness, but at times becomes inflamed and itchy, which will only last a day or so, but the rash is always there. It never goes away. What is it?