But despite the convenience, mixing something designed to go on your ends with something designed to go on your scalp doesn’t seem like the smartest thing to do. So what are 2-in-1s, exactly? “[The] technology is essentially a shampoo that has added silicones (a substance that coats the hair shaft, locking in moisture) and a suspending/bonding agent—usually glycol distearate—that keeps the silicones from separating out of the shampoo formula,” says Paul Wintner, hairstylist and global education manager for Alterna Haircare. But here’s the thing: A lot of shampoos add silicones, so the only thing differentiating 2-in-1s from some “regular” shampoos is marketing. “If you see a shampoo with the word ‘hydrating’ or ‘moisturizing,’ it probably contains the same ingredients that make a shampoo 2-in-1,” says Wintner. “[These] just add the gloss and anti-static properties for additional conditioning. The problem with shampoos without silicones is that they can work too well, leaving hair feeling dry and squeaky (which is why people need conditioner). The added conditioning from 2-in-1s prevents that dryness and makes hair more manageable.”
How do 2-in-1s work?
The key word here is silicones. If you’ve ever tried a new shampoo and marveled at the shiny aftermath, only to be left with stringy strands a few weeks later, that’s the result of silicones at work. They form a thin coating around your cuticle that keeps your hair hydrated and prevents frizz, but it can lead to some super annoying build-up over time. Why? Silicone’s coating properties prevent other moisturizing ingredients from penetrating into your hair shaft, so your hair can become drier. This causes your scalp to produce more oil to make up for the lack of moisture. But not all silicones are created equal. “Most common silicones used are very lightweight and don’t weigh the hair down,” says Wintner. These “good” silicones are typically water-soluble (e.g., dimethicone copolyol, stearoxy dimethicone, and behenoxy dimethicone). “Bad” silicones (e.g., dimethicone, cetyl dimethicone, and cyclomethicone) aren’t, meaning they will stay in your hair no matter how much you rinse.
So are 2-in-1s bad?
It’s all about the ingredients. Different silicones will give your hair different results, meaning the search for a good 2-in-1 will take some trial and error. If you have especially dry, brittle, or coily hair, they might not be the best option for you. Some emollients (read: conditioners) don’t have a good chance to moisturize the hair when paired with strong surfactants (read: cleansers), so you might find that a 2-in-1 doesn’t moisturize your hair as well as a leave-in conditioner might. Since silicones—even the “bad” ones—aren’t actually harmful, the choice to use a 2-in-1 product boils down to psychological preference. “Having bubbles in shampoo doesn’t make it clean any better, but people feel that it does,” says Angel Cardona, hairstylist and top artist for Sebastian Professional. “With a 2-in-1 shampoo, you won’t be getting that squeaky clean feeling, which some people need in their cleansing experience. But it’s still working the same way by removing dirt and oil.” If you prefer the silky feeling (or just the convenience), it’s completely fine to use 2-in-1 products. You just may need to add a clarifying shampoo once or twice a week. “The only downside to using a 2-in-1 is that the hair can begin to feel heavy over time,” says Cardona. “Occasionally alternating to a clarifying or exfoliating shampoo rather than a conditioning shampoo will let you reap all the benefits of silicones without the unwanted buildup.”
