Talk to Allergy Specialist on Dermatological

My father in law is having this allergy on his leg. Applied fresh aloe Vera gel and ice packs on it. It was red on day first with no blisters. Now blisters formed on that area but redness gets decrease. He is taking regix tablet too once in a day. No pain and no itching just redness and blisters. He is heart and bp patient also. And one more important thing this was due to rain water as it formed after coming home (during rain).

What's the reason and treatment for this? Kindly guide attaching pictures of before (without blisters ) and after