I would recommend that you go to see your doctors
">primary care doctor about this issue, especially as it has been going on for several years. The good news is that there is no itching or pain, which makes this less likely to be a serious medical problem. Nevertheless, I think that a good medical evaluation is in order.
There are several common potential causes of your reddened skin areas. The first is that this represents a form of chronic dry skin or eczema
. Sometimes this can develop slowly over time, such that itching or irritation are relatively minimal or not particularly bothersome. Nevertheless, it is usually pretty easy for your doctor to determine if this is what is going on and, if so, they can recommend various treatments, which might include moisturizing creams to the skin or even, in more advanced cases, topical steroid creams.
Another very common condition which affects the upper arms is something called keratosis pilaris, which involves plugging of pores in the skin with excess keratin. In severe cases this can give the entire skin area a reddened or inflamed appearance. Fortunately, this can usually be treated with some good moisturizing and gentle exfoliation, as guided by your doctor's advice.