Revised November 2, 2010
Remember the current limitations on carry-on luggage: No single bottle or tube can exceed 3.4 ounces (100 ml), the amount within the bottle or tube does not matter. If you have a specific product you want to take that is in a larger bottle, pack it in your checked luggage. But keep in mind that ultimately, you want to pack as light as possible, so before you put that big bottle in your checked bag, ask yourself if you really need it.
In local drugstores, you can find small plastic bottles that you can transfer your favorite shampoo, conditioner or lotion into and stay under the limit. When you assemble all of the items you want to take on board, they can not exceed the number you can fit into a quart plastic bag.
Whether it is in your carry on or in your checked luggage, it is good to double or triple bag and seal your cosmetics and other liquids and gels so that it does not leak into your luggage and onto your clothing. The bags will be useful for storing other items as you travel across Europe (though you may not want to use them for food storage.
Be sure to pack or buy sunscreen, especially if you will be visiting Rome or other parts of southern Italy, Greece, France or Spain in the summer. There is little shade in the Roman Forum or Coliseum, the Acropolis or the hilltop towns of Provence, so protect yourself from those burning rays.
If you forget sunscreen or other makeup, you'll enjoy a stop at a European drug store. US brands were common but many other options were available for sunscreens and lotions. I quickly realized how limited my choices were at home when I walked into a pharmacy that carried the full line of Loriel products as well as numerous other European brands with interesting formulas.