Along with the "do not remove" warning on mattress tags and the recommended serving size on potato chips bags, shampoo instructions are something many people ignore. Most hair-cleaning products will tell you to "lather, rinse, repeat," but as you may have noticed, skipping the "repeat" doesn't lead to disaster. So how did those words become standard on every shampoo bottle? Are haircare companies manipulating you into using more of their product, or is there a secret benefit to repeating that one-time shampooers are missing?
According to HuffPost, the question of whether to repeat or not to repeat largely depends on your lifestyle. The common line of thinking goes that the first lather removes any residue your hair has accumulated throughout the day—including dead skin, sweat, hair products, and environmental pollutants—while the second nourishes your hair and scalp. Some hairstylists claim that by skipping your second wash, you may be missing out on the moisture, protein, and other health benefits offered by your shampoo.
But this logic only applies to certain people. If you're washing your hair at least once a day—or even every other day—you likely haven't accumulated enough dirt to warrant a double-shampoo routine. Rinsing and repeating that often can actually have negative consequences, as it strips your hair of its natural oils without giving them time to build back up. Back-to-back washes make more sense for people who only wash their hair a couple of times a week.
What you do in between showers also impacts how often you should wash your hair. People who use products like mousse and gel, or who spend a lot of time in dusty or polluted environments, may benefit from shampooing twice a day. Scalp conditions like seborrheic dermatitis can also require repeat washes with a medicinal shampoo. The easiest way to figure out if you're washing your hair enough is to assess how it feels when you get out of the shower. If your scalp still feels oily or grimy, one wash at a time may not be cutting it.
Rinsing and repeating isn't necessary for most people, but the directions are still printed on most shampoo bottles. This may be a holdover from the industry's early days. When the first commercial haircare products appeared in stores, it wasn't typical for people to bathe every day. Telling people to shampoo twice whenever they did get around to it was good hygiene advice. Here are more fascinating personal grooming practices from history.