Are there any other possible causes of an itchy skin rash that resembles hives? (photo)

Sorry to hear that your child has developed hives after an episode of viral illness. I agree with Dr Colin Theng that a viral infection is most likely the trigger for this episode and antihistamines such as cetirizine would be the mainstay of treatment. I would usually optimise the dose of antihistamines for good control. If the maximum dose is still not able to control your child's hives, then a course of prednisolone may need to be considered. These medicines will help to switch off the activity of mast cells which have gone into overdrive, causing the appearance of hives.

It is not uncommon to develop dryness and itch after a trip to a cold country with low humidity. The dryness of the skin can aggravate the itch and can lead to the development of eczema. Hives can also be triggered by the change in temperature and climate. It would be useful for you now to use soap free washes and moisturize the skin regularly but if the dryness and scaling is persistent, you can visit the dermatologist who will be able help you with this problem. Hope you had an enjoyable trip to Europe!