Moisturizing shampoo is shampoo that tries to keep the pH of the hair at about its natural level, around 5.0 or so. When the pH of the hair gets too high, the hair becomes too alkaline, and the cuticles open, the hair becomes dry and brittle, and the shine disappears. Is the pH of the hair gets too low, on the other hand, it will become hard and rough. So a big part of moisturizing shampoo is aiming to keep the hair in that sweet spot between the cuticles opening too much, and the hair becoming too hard.
Of course, a moisturizing shampoo isn’t your only line of defense against dry and brittle hair. A good conditioner will help heal any damage you may have caused with a rough shampoo, and help to replenish some of the oils that you’ve stripped away with your shampoo. On the other hand, conditioner can only go so far, so the less damage you can cause, preferably by using a good moisturizing shampoo, the healthier and more vibrant your hair will be in the long run.
These days, most brands advertise as being moisturizing, so you’ll want to look at the ingredients to get a better feel for whether they will actually help your hair. First and foremost, you want to look at how many sulfates the shampoo includes. Sulfates help shampoo do its primary job, removing dirt and gunk from your hair, but they can also remove too many of the natural oils from your hair, making it overly dry. A good moisturizing shampoo has a single sulfate in it, but anything more than that and it is designed to strenuously cleanse hair, not to moisturize it. There are a wide range of sulfates used in shampoos, but some of the most common are sodium laureth sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, and ammonium laureth sulfate.
Both ammonium lauryl sulfate and ammonium laureth sulfate are particularly harsh on hair, designed to clean especially dirty hair, not to moisturize. Similarly, if faced with a choice in your moisturizing shampoo, the laureth sulfates are gentler than the lauryl sulfates, and sulfates like tricedeth or sodium myreth are even gentler still. Shampoo that contains sodium myreth, in particular, will tend to be much more focused on moisturizing your hair.
Of course, shampoo isn’t much good if it isn’t cleaning your hair. So it’s important that there be something the shampoo doing its job. Once you cut out sulfates, either most or all of them, you’re left with a few options for gentler cleansers that indicate you’re using a truly specially-formulated moisturizing shampoo. Lauryl polyglucose, isethionate, and cocamidopropyl betaine are some of the most common of this gentler class of cleaners, or surfactants.
One last thing to look out for are the relative amounts of ingredients in your shampoo. Many manufacturers have become savvy to the fact that their consumers now know ingredient lists cover ingredients from most to least, by law. So what they will do is include all of the herbal and plant-based ingredients at the top of the list in a long grouping, ending it with “in water” or “in purified water”, which makes the quantity much larger because it is in water, when in fact there is likely very little of these ingredients present. Take care to look further down the list to look out for sulfates anyway, and don’t be fooled by the presence of jojoba or ylang ylang into thinking you are buying a gentle moisturizing shampoo.