How Can Arm Rash Marks With Itching Be Treated?

I got a rash on my arm, sort of like eczema (though ive never had it before), that has slowly gone now, however, on my underarms, ive noticed red marks. They are small and circular and raised, but not like spots, almost like dry skin, and i thought i might just have alot of ring worm, but it 100% isnt that, but its all over both of my underarms and it itches like mad. I was just wondering if you knew what it was, and if it was serious, because I know that being a woman, things under the armpit can often still be realted to the breat area, and being a hypochondriac, i always fear for the worst. Please can you help me?