Skin rashes. Relieved from this rashes?

I've been getting skin rashes mainly on my forehands & stomach. These rashes generally appear in evening and increases at around 9 or 10pm. I had tried allopathy doctor last year and he did some blood test all being negative. He suggested taking ketasma (half tablet) twice for 3 months. I tried it but it didnt work. Once the dosage was stopped, it reappeared. I tried Ayurvedic medicines, and after 1.5 months of this course, it looked the medicine worked. I was relieved for almost 6 months. However, recently now I am facing the same problem again. I have reached out to Ayurvedic dr. again but have got tired of dealing with it. When the rash becomes intense, I take citrizin tablet (5mg) and again the rashes disappear for 3-4 days. Can you suggest which doctor should I try out for permanent solution and how can I get relieved from this rashes?