Hairdryers in Spain and Italy

You would have found out that no it won't.. Hehe, I read this late.

For anyone else, the voltage here (europe) is 230vac, so you'll need a transformer. However, most hotels have a hair dryer in the bathroom (in Italy).

Do not take your US 117V hairdryer to Europe where the voltage is 235V.
Buy a cheap one there. It will for sure last for your stay. And after it, throw it away, because it will be useless in the US.
A 400W US hairdryer would, if connected to the European electrical network, produce 1600W. For a short while (10 seconds maybe). Then it will throw out a lot of flames.
That is, if the plug would fit. But it won't.
Or, just as simple, let your hair dry in the sun.

Letting your hair dry in the sun is a fine simple answer... However, if you want to dry your hair in an unnatural way, first purchase a power ADAPTER - this converts the narrow USA plugs into the round or otherwise European ones (this will cost no more than a few dollars), but this converts ONLY THE SHAPE, not the power itself. THEN, purchase a dual voltage travel hair dryer. These can be found easily online. If you read the fine print on the plug end of the power cord it must include something that says 110-240v AND 50-60Hz. European power is generally 240v or less and 50Hz (whereas US power is 110v and 60Hz). Either way, a dual voltage hair dryer should cover either of these. Some of these appliances have a switch to change back and forth between the two voltage types. If you have it on the wrong setting, you will be buying a new one or letting your hair dry in the sun...