Key ingredients: biotin, pro-vitamin B5, coconut oil, saw palmetto berry extract, loquat fruit extract | Scent: cardamom, pineapple, tangerine, lavender, bamboo, blonde woods

Best for Flat Hair: Bumble and Bumble Thickening Volume Shampoo

Why it's worth it: Even if you have naturally thick hair, it can become prone to flattening due to the weight of buildup, oil, and your overall hair texture and pattern. If that’s the case for you, Rotger recommends the Bumble and Bumble Thickening Volume Shampoo, which she calls an “O.G. thickening shampoo that never fails to provide that extra volume.” This shampoo washes away product buildup that’s weighing down roots so they can rise, making hair appear more voluminous. It’s also spiked with moisturizing antioxidant panthenol to allow strands to reach their bounciest, smoothest potential.

Key ingredients: panthenol | Scent: lemon, bergamot, apple, water lily, white musk, cedarwood

Frequently Asked Questions

What should fine hair types consider when looking for a new shampoo?

When looking for a shampoo to thicken hair, first consider what to avoid. Fine hair types should look for formulas that won’t weigh down your hair, says Rotger—so heavily-moisturizing formulations are a no-go. It’s also helpful to avoid heavy silicones or oils, which also weigh the hair down and make it look flat, according to Giannetos. “A good shampoo should add lift while still being gentle enough for everyday use,” he says.

Now, what you do want to look for in your next shampoo, according to Korab, are ingredients that provide lightweight moisture and promote fullness. “Look for ingredients like rice protein, biotin, or panthenol to add strength and body,” she says. If you have color-treated hair, Korab suggests opting for a sulfate-free shampoo to preserve your shade—as sulfates are notorious for fading color—without compromising volume.

How else can I make my hair look thicker?

Post-shower styling is truly the key to creating fuller, more voluminous hair. “Start with a volumizing mousse or root lifter to give lift right at the scalp,” says Giannetos. “Blow dry with a round brush to build body, and finish with a lightweight texturizing spray for fullness without weight.” A deep side or zig-zag part can also add instant dimension, according to Korab, while velcro rollers or a hot air brush enhance volume. But if you want the fullest, thickest-looking hair of your life, she says to give clip-in or halo extensions a try. (Just make sure you use extensions sparingly, as they can exacerbate fallout.)

Meet the experts

• Natalie Rotger, a hairstylist and colorist at Jenna Perry Hair in New York City
• Jennifer Korab, a hairstylist based in New York City and New Jersey
• Dimitris Giannetos, a hairstylist and colorist based in Los Angeles

How we test and review products

We always enlist a range of testers for our makeup vertical, but hair-care products and tools are another story. While there are certainly products that can be used across different hair textures, lengths, curl patterns, thicknesses, colors (natural and unnatural), and needs, hair products are often created with specific consumers in mind. Many are created in order to address a concern (dandruff, breakage, brittleness) or to work most effectively for a specific hair type (4C curls, wavy hair, gray hair). You wouldn't want to pick up a purple shampoo that’s only been reviewed by someone with, say, auburn hair, or a diffuser that’s never been tested by anyone with curls—right?