What Causes Rashes From Knees To Ankles After Recovering From Breast Cancer?

I am 65 years old , a breast cancer survivor since 2002, on no medications except Vitamin D3 5 6 and 162 pounds. For the last five or six years whenever the weather turns warm, I get rashes on my ankles , knees and sometimes calf areas. The rash starts as a small itchy/burning speck and radiates outward until it looks like a target. After I wash it with Hypercleanse and calamine lotion a few days it starts to stop itching and gradually fades away. It recently appeared on the tops of my hands . I have been tested for Lyme s disease and it was negative. I don t have this problem in the fall and winter. Can you give me a clue as to what causes it? I don t have pets and I only go outside to get into my car.