Hello, Welcome to HCM, The typical description that you mention dark, discoloured and dirty looking and the location upper arm, both arms almost points in the direction of Macular Amyloidosis. It is difficult to confirm the diagnosis without examining the affected area though. Eczema or dermatitis is quiet rare on upper arm especially with this symmetry and on both sides. I would suggest following daily regime that helps with Dermatitis as well as Amyloidosis. 1. During bath avoid scrubbing or using a loofah as it can aggravate the condition (Amyloidosis as well as Dermatitis). Use a moisturizing body wash instead of soap. 2. Use a body lotion containing skin repairing ceramides immediately after bath and once in the evening. 3. Use a broad spectrum UVA/UVB sunblock with PA++++ daily in the morning and afternoon. 4. Have a diet rich in omega 3 (fish, nuts, canola oil) and antioxidants (colourful fruits & vegetables, dark chocolate, red wine) When you follow this regime, you will notice some improvement within 2-3 weeks. If the improvement is not significant then you could consult a Dermatologist and get a prescription strength topical steroid and consider Pyruvic or Light Phenolic chemical peels. For more information you can read All About Sunscreens, Diet for Glowing Skin, Pigmentation and Skin Lightening at www.dermatologydiaries.com Keep Looking Beautiful Dr Niketa Cosmetic Dermatologist Mumbai, India