Suggest Remedy For Skin Ailments

Hello I am 15 years old and I have had odd reoccurring brown patches on my forearms, neck, legs, and ankles for a year now. I have been able to scrub the ones on my arms off but no matter what I do to the others they just stay there! my mom thinks it's just dry skin but it's not itchy or anything... Can you help shed some light on this? Thanks