The Best Hair Serums, According to Beauty Scientists

 Serums are the do-it-all heroes of hairstyling products. These formulas fall under the umbrella of leave-in conditioners and are mainly intended to help frizzy hair stay smooth under humid conditions (especially sticky summer days). Though traditionally created to keep hair sleek, some hair serums now address styling needs for different hair types (fine, medium, thick), help with hair damage or loss, or enhance hair texture (wavy, curly, or straight).

The Good Housekeeping Institute Beauty Lab evaluates hair serums on how well they prevent hair from forming frizz under humid conditions. In the Lab, human hair samples are pretreated with standardized shampoo and other products plus the serum, then exposed to a gradual increase in humidity for 24 hours. Hundreds of consumer testers around the country also evaluate the hair serums at home, reporting back on the product's attributes, ease of use, and effects, including look and feel of hair after use. (The Lab's most recent hair serums test included 347 consumers evaluators!) Both sets of data are then tallied to find the top-performing hair serums.

Here, the GH Beauty Lab's top-tested and expert-recommended hair serums for everything from smoothing and straightening strands to fighting frizz, volumizing thin hair, stimulating hair growth, combating split ends, and more