What Causes Red Rash On Ankle?

hi dr iam 45 years old, i have hight blood pressure and iam on tablets 5mg amlodipine, iam about 5,4 and about 13stone, i have developed a rash on my right ankle it looks like freckles but red, thay are not itchy. i used to take water tablets but i dont now i was wondering if it could be any thing to do with water