This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Eczema and related disorders, Subject name: Dental
A 63 year-old obese woman who has suffered from chronic leg swelling for several years. Her legs get intermittently red and swollen. When this happens she applies a combination of lanolin and Neosporin. One week ago, she did this and her legs got very inflamed and developed blisters, oozing and severe pruritus. The most likely diagnosis is: 
Select and explain. 
A. Allergic contact dermatitis, B. Bullous Impetigo, C. Cellulitis, D. Erysipelas
A: Allergic contact dermatitis
Answer: A: Allergic contact dermatitis 
Explanation: Allergic contact dermatitis of the lower legs is usually caused by topical medication.