What's your hair type? Different types of hair call for different types of shampoo. For fine, limp, or oily hair, you should opt for a clear shampoo that can scour the excess oil from your scalp without weighing down your tresses. A dry shampoo is often a good choice for this hair type, since it absorbs excess oil and adds volume. By contrast, dry hair – which includes almost all curly hair – needs a product that cleans gently without stripping away all the hair's natural oils. Look for a thicker, creamy moisturizing shampoo with ingredients such as shea butter, plant oils, or silicone to coat the hair shaft and keep moisture in.
How often do you shampoo? Some shampoos – particularly those labeled as deep-cleaning or clarifying shampoos – are too harsh to use daily and are instead designed for once- or twice-weekly use. That doesn't mean you can't use them as needed to clean away oil and the residues of styling products; you should just plan to alternate them with a different shampoo that has a gentler formula. If your hair is curly, dry, or damaged, you might want to consider going longer between washings, as even a moisturizing shampoo can dry out the hair somewhat. Julyne Derrick, the beauty expert at About.com, recommends simply rinsing your hair with water and following up with a conditioner.
Is your hair color-treated? Sulfates and other ingredients found in many shampoos (particularly clarifying shampoos) can strip hair of color. While there are shampoos specifically formulated for color-treated hair, experts say you don't really need these products to get good results. Look for gentle, sulfate-free shampoo or opt for a baby shampoo.
How delicate is your skin? If your skin is especially sensitive, you'll need to steer clear of harsh ingredients that can cause irritation. Non-irritating ingredients are also important in a baby shampoo, since babies' skin tends to be delicate. According to the "Skin Deep" cosmetics guide from the Environmental Working Group, common irritants in shampoos include methylisothiazolinone, methylchloroisothiazolinone, and benzisothiazolinone. Fragrances can also cause problems for some people, so if you're having trouble finding a shampoo that doesn't bother your skin, a fragrance-free product could be your best bet.
Do you object to animal testing? The companies that make many shampoos on your drugstore shelf – including Unilever, L'Oreal, Johnson & Johnson, and Proctor & Gamble use animals to test the safety of their products. If you have a problem with that, you can look for shampoos labeled as "cruelty-free," which are tested in ways that don't involve animals.
When you're choosing a shampoo, experts warn against being taken in by misleading product claims. For example, there is no such thing as a shampoo that can repair, restructure, or nourish damaged hair. Hair isn't alive the way skin is; once it's left the follicle, any damage done to it is permanent, and the only way to undo it is with a pair of scissors. Shampoos can improve the look and feel of damaged hair, but only temporarily. Other claims on a product label, such as "moisturizing" or "volume-boosting," may be accurate, but they're not regulated by the Food and Drug Administration, so you get no guarantees. And one piece of advice on the label that you should definitely ignore is "Lather, rinse, repeat." Unless you use an unusually large amount of styling products, experts say it's only necessary to lather your hair once, using about a quarter-sized dollop of shampoo (or dime-sized for short hair) and slowly massaging it into the roots.