Ankle rash could be caused due to various reasons including - dermatitis, dry skin, eczema, heat rash
or sweat dermatitis, uncomfortable footwear, etc.
It is important to wear lose comfortable footwear and maintain good personal hygiene. Use a powder to avoid sweat collection and apply calamine lotion at the sites of the lesion.
You could take oral antihistamine or antiallergic medications for the itching. Apply calamine lotion at the sites.