Problem: I've been following your advice and am using products from several different lines. My skin is doing well, but all the cosmetics salespeople say it is a mistake to mix and match. They say products are designed to work together, and that is what helps the skin best.

Solution: Stop listening to those cosmetics salespeople; they are wrong. If every line had SPF 15 sunscreens with the requisite UVA protection, gentle cleansers with nonirritating ingredients, foundations that aren't peach-colored, and on and on, I would agree that you don't need to mix and match. But I have found good and bad products in every line. Many lines don't have adequate sunscreens, while they do have products that contain irritating ingredients, or offer rose, peach, and ashen foundation colors, or make mascaras that flake and smear. If you only buy products from one line, chances are that you will end up with some bad products! Mixing and matching is the only way to go. You don't wear clothes from one designer, buy furniture from one manufacturer, take medicine from one pharmaceutical company, or eat food from just one company. The only way to develop a successful skin-care or makeup routine is to select what works best for your skin type and needs, not because it's from a particular line.