Hello, This is dr. Papaqako answering your question. Nexium does not contain sulfur, and its from another category from the drugs that your husband has an allergy from. Some people have a tendency to acquire some type of allergies and become sensitive to some particular allergens. These allergies may resolve by themselves, or become worse with the time. Main treatment of these allergies is to avoid the allergen. I don t think that your husband has an allergy from Nexium, because its not of those drugs that cause allergy. If I was your caring doctor, I would recommend to consider doing an examination called FGS (fibrogastroskopy) that may discover or rule out other causes that might have caused Nexium not to be effective for GERD, like a complication of it with an ulcer or other. Hope this helps, Take care.