Is it ok to take diphenhydramine, which prescribed by one physician, with hydroxyzine, prescribed by

Diphenhydramine and hydroxyzine may be taken together but the patient should be monitored for potential side effects, as there is a moderate drug interaction.

As both the doctors who prescribed these medicines individually aren't aware of the concomitant use, they won't monitor your husband. Please make at least one of the doctors aware that he has been given (or taking both these medicines) and they can decide whether they want him to take just one or both, and if they do want him to take both then they will monitor him, at least initially.

To see full details of the interaction please see link below.

http://www.drugs.com/drug_interactions.php