Bored kids read cereal boxes. Smart women read shampoo bottles.

While products like hair color and styling gels command greater attention, choosing the wrong shampoo can have a serious impact on how your hair looks. You’ll never achieve the result you want if you buy the wrong shampoo—or use the right one incorrectly.

It all starts with shampooing frequency. And with a penchant for cleanliness, Americans tend to overwash their hair.

"The hair and scalp should be cleaned, on average, every other day," says Dr. Andrea Lynn Cambio, a board-certified dermatologist in New York City.

But women with exceptionally dry hair, such as African-Americans, need to reduce shampoo frequency. Conversely, if you have incredibly oily hair, daily shampooing may be required to cut the grease.

"The consequence of overdoing it is stripping the hair of sebum [oil]," Dr. Cambio tells Stellure.com. "This causes the hair to look dull, feel coarse, be prone to static electricity and be a styling nuisance."

Shampoo & Your ’do

By definition, shampoo is designed to remove dirt and excess sebum from the scalp and hair. Sebum is necessary for hair health. It is secreted by sebaceous glands, found in skin all over our bodies, including the scalp. These glands provide healthy lubrication to our skin and hair. Scientists estimate that the average woman produces approximately 1 ounce of sebum every 100 days, so it’s a substance worth protecting!

If you have oily hair, your sebaceous glands secrete too much sebum, and you’ll want to select a shampoo designed to control it. If you have dry hair, your glands secrete too little sebum, and you’ll want to choose a shampoo that provides extra moisture. If you have “normal” hair, sebum production is how Goldilocks described her final bowl of porridge: “Just right!”

While Goldilocks may have been a porridge expert, it’s hard to say whether she knew how to choose the right shampoo for her specific hair type. Gentle shampoos, like baby shampoo, remove the bare minimum. Harsher shampoos, like dandruff shampoos and those made for oily hair, are manufactured to cleanse more thoroughly and remove more sebum. Problems typically occur when, for example, a woman with oily hair accidentally buys a shampoo intended for dry hair. She may not discover why her scalp has become an oil slick until she checks the shampoo bottle.

Understanding Labels

As with food products, ingredients in shampoos are listed by the amounts contained in the bottle, in descending order of weight. The higher up on the list, the more of the ingredient in the shampoo.

Normally, the first ingredient in shampoo is water. If it, alone, could cleanse the hair, we wouldn’t need shampoo. Water, however, cannot remove oil, sebum or product buildup, so manufacturers must add detergent agents known as “surfactants.”

Surfactants cleanse the hair and create lather. Manufacturers can choose from inexpensive or pricey surfactants, and these generally determine the quality of your shampoo. Cheap surfactants, such as sodium lauryl sulfate and ammonium lauryl sulfate, are popular among manufacturers because they keep down costs. You’ll find these particular surfactants in generic, supermarket, drugstore and certain mass-market brands. (They’re also the chemicals most commonly associated with eye irritation.) The problem, however, is that these surfactants are harsh on hair, stripping it of oil and causing hair color to fade more quickly.

The more expensive “designer” or salon brands contain more expensive surfactants, such as sodium cocoyl isethionate and methyl cocoyl taurate (sometimes labeled simply as “coconut oil” or “fatty acids”), cocamidopropyl betaine and cocamidopropylamine oxide. Yes, they’re certainly a mouthful, but they are nondrying, much more gentle on the hair and tend to work well regardless of whether you have hard or soft water. They’re also more expensive for manufacturers to use, so that’s why you’ll pay more for a bottle of shampoo. (Many manufacturers compromise, mixing low-cost sodium lauryl sulfate with a coconut-oil surfactant. This can work well.)

Some shampoos contain detanglers and anti-static agents, which function exactly as their names imply. A common agent to look for is “quaternary ammonium.”

“Humectants” behave like tiny sponges, attracting and holding water. You’ll find them in shampoos for dry, damaged or color-treated hair. Commonly used humectants include glycerin, sorbitol, sodium lactate and hyaluronic acid.

“Conditioning agents” help soften hair and allow it to retain moisture. Look for amino acids, collagen, panthenol, elastin and proteins on ingredient lists.

“Thickening” or “volumizing” shampoos increase bulk and improve manageability. They contain ingredients like hydroxyethyl cellulose, gum arabic, guar, xanthan and chitin. One of the newest products on the market is Aveda’s Pure Abundance Volumizing Shampoo, which contains coco/babassu sulfate—a substance derived from organic coconut and babassu oils. Shane Wolf, Aveda’s executive director of global hair care marketing, recommends it for the “one-third of American women who describe their hair as naturally fine or limp."

“Preservatives,” such as methylparaben, quaternium-15, methylisothiazolinone and propylparaben, help prevent shampoo from becoming contaminated by mold or bacteria. “All-natural” shampoos that contain no preservatives have a tendency to “spoil” if not used within their designated shelf life.

Never buy a shampoo based on its fragrance, which is no reflection of a shampoo’s quality. It’s only one more ingredient manufacturers use to convince you to buy their products. (Who doesn’t open the cap and sniff before buying a shampoo?)

What’s Best for You?

Since each of us has individual needs, experiment with different shampoos to determine which ones make your hair most manageable.

Many women fail to take their hairstylists’ recommendations on shampoo, assuming the stylist is “ripping them off” or “trying to sell them something” so the salon can make more money. In reality, stylists know that salon-quality shampoos are generally superior to their drugstore counterparts. If you trust your stylist, it’s worth taking her advice. The worst-case scenario: You won’t like the product, and you can express your disappoint to her.

If budget is a problem and you simply cannot bear the thought of spending $10 to $15 for a single bottle of shampoo, dilute the $3 brand you’re currently buying (one part water to two parts shampoo). This will reduce the harshness.