Come on ... fess up. You feel guilty using 99-cent shampoo because it's really bad for your hair. Anybody knows the $24 salon variety is so much better, especially for chemically treated hair, right? Wrong!

Price has nothing to do with it (and I tell you this at the risk of getting angry letters from professional hair dressers and salon owners).

Fact: All shampoos are up to 80 percent water. The rest is detergent with a few drops of fragrance, additives and preservatives.

Fact: There are basically two kinds of detergent: anionic (harsh) and cationic (gentle).

Fact: The only part of the shampoo bottle that's regulated by the Food and Drug Administration is the list of ingredients. Manufacturers can make any claim they like on the unregulated portions of the label. Sometimes the hype has some merit; often it has none.

The secret to shampoo intelligence is to know your detergents. Pay little attention, if any, to anything on that bottle or packaging except for the list of ingredients. Water (or some fancy name for good old H2O) will always be the first ingredient. Next comes the detergent. Here are examples that you might find, as well as the effect they have on your hair, according to the Bellatory website:

—Ammonium lauryl sulfate — very harsh

—Ammonium laureth sulfate — harsh

—Sodium lauryl sulfate, or SLS — still harsh

—Sodium laureth sulfate, or SLES — mild, great choice

—Triethanolamine lauryl sulfate — gentle, good choice

—Triethanolamine laureth sulfate — gentle, good choice

Myth: Shampoo builds up on hair, so you need to change brands occasionally to counteract this. Shampoo cannot build up on hair, however, conditioners and other products and chemical processes do, and you may need to use a stronger type of shampoo from time to time.

Myth: Salon-brand shampoos outperform inexpensive store brands. Not true. Salon brands may have more fragrance, foam or ingredients, but all of it goes right down the drain with the detergent.

Myth: High-quality shampoo can repair and nourish damaged hair. Hair is dead and cannot be repaired. Any hair product can only provide temporary benefits to the look and feel of hair.

Myth: Baby shampoo (no tears) is great for adults because it is so gentle. The detergent in baby shampoo is way too gentle and not designed for cleaning adult hair, especially when a lot of styling products have been used.

When purchasing shampoo, consider just two things: price and type of detergent.

Interestingly, the "rinse and repeat" instruction you will read on every shampoo bottle goes back to a marketing campaign one manufacturer created to increase sales. It does that, all right. You can make your shampoo last twice as long if you skip the repeat.

Rinse thoroughly. If your hair turns out dull and lackluster, the problem may be inadequate rinsing. Tip: Pour 1/2 cup white vinegar through hair during the rinsing process. This will remove all traces of the shampoo and leave your hair sleek and shiny.

If you clip shampoo coupons and match them with shampoo sales in your grocery store, you may never pay more than $1 for shampoo again.

Hint: Many shampoos in the Herbal Essences and Suave lineup — found in most supermarkets and drug stores — contain the gentle option sodium laureth sulfate. Just don't assume. Read the label.

With the money you save on the shampoo, buy a quality conditioner. Unlike shampoo that washes down the drain, the quality of conditioner does make a difference.

Mary invites questions, comments and tips at mary@everydaycheapskate.com, or c/o Everyday Cheapskate, 12340 Seal Beach Blvd., Suite B-416, Seal Beach, CA 90740. This column will answer questions of general interest, but letters cannot be answered individually. Mary Hunt is the founder of www.DebtProofLiving.com, a personal finance member website and the author of "Debt-Proof Living," released in 2014. To find out more about Mary and read her past columns, please visit the Creators Syndicate webpage at www.creators.com.