What Exactly Is "Hair Filler" and How Does It Work?

Oct 02, 2023

By Jeannine Morris Lombardi

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When it comes to hair-care terminology, the meaning behind the phrase "hair filler" isn't so cut and dry. What began as a term used by colorists is now often thought of as a product, enhancement, or treatment that helps to make your hair appear fuller — or in some cases, actually become fuller.

The origins of the term start with how colorists "fill" hair with appropriate colors when they want to deepen a client's tone. As Brendan O’Brien, a colorist at Lamb & Wolves in Red Bank, New Jersey explains, "If you dyed your dark hair to a level 10 (or platinum) blonde and want to go back to brunette, you need to fill your hair with the color molecules that have been stripped away." The process is a science that only a professional colorist can truly accomplish.

However, today we're seeing a slew of new products marketed as hair fillers thanks to their bond-building ingredients, and the term is tossed around by hairstylists and dermatologists alike. From strategic extension placement and keratin-infused treatments to permanent solutions for baldness, hair fillers today are about all things fullness.

Whether you have fine or damaged hair, a receding hairline, or just want added thickness, there's a hair filler solution for you. "When you really break it down, there's a hair filler technique or product out there for everyone looking for added fullness," says Jan Marie Arteca, a colorist at Sally Hershberger. "The right one for you really depends on your needs, budget, and lifestyle."

With that said, we found the best type of hair filler for your specific need.

Stylists have long used keratin bond extensions as a semi-permanent way to add volume to fine or thin hair. Extensions are applied strand by strand, and then heat is used to fuse the bond to your hair at the root; it lasts about three months. Arteca is also an extension specialist and explains that the key to using extensions as hair filler is to strategically place them where the hair is finest. For example, most of her clients need a few by their temples — or if she's doing a full head, she places more in that area than in other places to help fill out the face frame.

Warning: In-salon keratin-bonded extensions are timely and pricey, ranging from $1,500 to $3,000 for a full head. If you're looking for a more affordable way to use extensions as hair filler, try using clip-ins, like pieces from Hairdo 22" 4PC Wavy OR Straight Fineline Extension Kit, where needed. The brand makes clip-ins in many different shades and textures that you can have your stylist cut for specific hair length, so they'll blend seamlessly. Hidden Crown Hair Halo Extensions are known as red carpet staples, as well.

Although there are several different in-salon treatments that can help repair the bonds in your hair, Olaplex created the category in 2014 and is still hailed as a hero. It's a two-step process that uses a bond-building technology to penetrate the hair shaft and help rebuild it from the inside out. Ron Robinson, cosmetic chemist and founder of BeautyStat, explains, "Healthy hair looks like shingles on a roof lying flat upon each other. When your hair is damaged from over-processing, heat, or lack of care, the shingles begin to lift apart from each other and eventually fall." The patented chemicals in Olaplex have his stamp of approval for "filling in" and repairing the damage because they can work deeper into the hair's cortex and repair broken bonds by reconnecting them.

Olaplex also makes at-home products such as the famous Hair Perfector No. 3, a weekly treatment that helps to repair your hair. More brands have jumped into the bond-building game recently, which means you have options. We like the OGX Restoring + Bonding Plex Bonding Cream and Orlando Pita Play Former Glory Protein Treatment Spray.

Whether you have a fine hairline, suffer from hair loss around your temples from pregnancy or stress, or find that your part is starting to recede, this is the hair filler solution for you. "The industry go-to is Toppik," states Arteca. "It's super low-maintenance and it's so easy to use that you can do it every day or just for special events."

Toppik is a spray-on hair powder that comes in nine shades and contains keratin and silica that form small hair fibers that attach to your natural hair fibers. "When you brush the powder onto your hair, the ingredients collect onto themselves and then onto your hair like a magnet," explains Robinson. Besides helping to camouflage bald spots or fill in your hairline, Toppik also helps to create density, body, and texture. Style Edit Root Cover Up Stick and Color Wow Root Cover Up are also both powder formulations that get the job done.

"In dermatology, people often look at platelet-rich plasma (PRP) as hair filler," states Adriana Lombardi, MD, a board-certified dermatologist at The Skin Cancer and Cosmetic Surgery Center of New Jersey. "My patients are interested in PRP for many different reasons including as an attempt to stop hair loss, regrow their hair, or to try to make their hair fuller."

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The treatment involves having your dermatologist draw your own blood from your arm, which is then put into a centrifuge that separates red blood cells from plasma. That plasma contains platelets, which are injected into the scalp to promote hair growth. Neil Sadick, MD, a board-certified dermatologist in New York City, previously told Allure that PRP is "a great treatment option for hair loss because it has a number of scientifically based articles showing its efficacy increasing hair count, hair thickness, and the growth phase of the hair cycle."

But it won't come cheap: Dr. Lombardi recommends three to four sessions of PRP (which costs about $1,800 total) with touch-ups every six months as needed (at $800 a pop). Lately, she's been seeing many patients who have experienced ongoing hair loss due to COVID. According to a recent study, COVID is responsible for acute telogen effluvium, or hair loss triggered by a stressful event that lasts up to six months. Dr. Lombardi recommends that if you've been experiencing hair loss for over three months, consult your physician for blood work to make sure there aren't underlying factors causing it such as a hormonal imbalance.

Ultimately, experts agree that hair filler is a loose term and takes on many different perspectives. No matter how it's defined, the mission is clear: Hair filler can boost your confidence. Think fuller, shinier, healthier strands… at least temporarily. If you're still unsure of the best hair-filling treatment for you, start by consulting your hairstylist. Be specific as you state your concern so that they can guide you towards the best approach for fuller-looking hair. After all, that's what experts are for.

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