Old man with diffuse itchy rash

90 y.o white gentleman with h/o HTN, HLD, COPD and GERD is admitted to the hospital for progressive epigastric discomfort and a sensation of food sticking in his lower esophagus. In addition, he has also noticed a red itchy rash for the past few days that has been spreading from neck to toes. He denies fever, malaise, weight loss or arthralgias. He denies any change in laundry detergent or soaps. He meds are also unchanged, which include Atenolol, Diovan, Ambien, Omeprazole, Mylanta, Milk of Magnesia, Xanax, Albuterol, mucinex, Senna, Tylenol, Vitamin D and Calcium. On exam, his vital signs are stable. Diffuse circumscribed rash that is raised and erythematous is noted. The patient received a combination of anti-histaminics (H1 & H2) as well as steroids. His rash completely resolved by the next day. Which one of the following is the most likely diagnosis?

A. Urticaria
B. Morbilliform drug eruption
C. Severe atopic dermatitis
D. Erythema multiforme
E. Pityriasis rosea