We’ve Tested Everything—Trust Us When We Say These Are the 8 Best Shampoos for Volumizing Fine Hair

So, here's the thing: Hair-thickening shampoos can temporarily plump up your strands for fuller-looking hair, but you can't *actually* thicken fine hair strands or make them grow in denser. As trichologist Gretchen Friese previously explained to Cosmo, this is because "the thickness of the hair most often is determined by the size of the hair follicle," and no matter what kind of shampoo you use, you can't alter the chemical structure of your hair. Sry, blame genetics!!

Btw, having "thin" hair doesn't necessarily mean you have "fine" hair, and the two terms shouldn't be used interchangeably. "When referring to fine hair, what you’re really talking about is the texture and density of each individual shaft of hair," hairstylist Adam Federico previously told Cosmo, while thin hair refers to the number of strands on your scalp. That said, both fine and thin hair types can benefit from using a thickening shampoo that adds body and increases the appearance of fullness.

Sad fact of life: Finely-textured hair tends to become greasy more quickly and requires more frequent washing. According to dermatologist Iris Rubin, MD, those with finer, straighter hair types generally need to suds up more frequently than those with coarser, curlier hair types, who can generally go longer between wash days. For fine hair types, skipping more than a day between washes could lead to product buildup that weighs strands down, making your hair look flat or oily (or both!).

And buildup doesn't just give you sad, limp hair. The accumulation of buildup can lead to dandruff, irritation, and even hair loss. "The follicles on your scalp are literally the manufacturing plant for your hair," Dr. Rubin previously told Cosmo, "so for your best hair health, it’s important that they don’t get clogged." Some experts even recommend washing fine hair daily—but if you do decide to wash every day, make sure you're using gentle, sulfate-free cleansers filled with hydrating ingredients and following up with conditioners.

Check out the ingredients.

If you're someone with thin hair that could use a lil oomph, you'll ideally wanna choose a shampoo that contains both volumizing and fortifying ingredients, such as biotin, panthenol, keratin, peptides, and thickening polymers, which will help to plump and strengthen fine strands.

And even though some heavy oils—like olive oil and castor oil—can help you achieve better hair health, it's better to stick with lightweight hair oils, especially if you're someone with low-porosity hair. For instance: Moroccanoil Extra Volume Shampoo uses lightweight argan oil to coat brittle strands.

Skip the sulfates and silicones.

Listen, sulfates have a time and a place, and while some people can actually benefit from using sulfated detergents, it's probs best to skip 'em if you're experiencing hair loss. ICYDK, sulfates are harsh surfactants that can strip away your hair and scalp's natural oils, so those with fine hair should typically steer clear. Likewise, silicones are great for giving hair slip and shine, but they can also weigh down finer hair. Opt for lightweight, smoothing alternatives like jojoba and sunflower seed oils.

Choose a formula that promises volume or thickness.

When you have fine, flat hair, one of the most important things to look for in a shampoo are words like "volumizing" and "thickening"—though ofc, it helps to know what ingredients actually work to plump strands. Look for products with biotin, amino acids, hyaluronic acid, peptides, or niacinamide, as these all work to strengthen follicles and help your hair shaft hold on to more moisture.

• Gretchen Friese is a certified trichologist, as well as salon director and hairstylist at Foushee Salon Spa in Littleton, CO.
• Adam Federico is a hairstylist, educator, and VP of creative development at R+Co.
• Dr. Iris Rubin is a board-certified dermatologist and the founder of Seen Hair Care.

Corinne Sullivan is an editor at Cosmopolitan and has six years of experience writing about beauty, fashion, and lifestyle news, including the best dry-scalp shampoos and the best-smelling shampoos. She regularly tests and analyzes shampoos on her own fine hair for efficacy, and she works with the industry’s top dermatologists, hairstylists, and trichologists to assess new formulas and brands.

Beth Gillette is the beauty editor at Cosmopolitan with seven years of experience researching, writing, and editing skincare stories.