Human hair is comprised of a cuticle layer and an inner cortex that is predominately made up of proteins called keratins. Keratin is responsible for making hair strong and providing flexibility to prevent breakage. Our hair becomes brittle and easily damaged when these keratins are injured by our environment and even our styling choices (like blow drying or heat styling).

However, bleach treatments are one of the worst offenders when it comes to degrading the integrity of our hair's keratin. So, what can be done to repair the hair proteins? Enter: protein filler treatments.

• Tatum Neill is a hairstylist and the Creative Director of Aveda Arts & Sciences Institute.

• Ava Shamban, MD, is a board-certified dermatologist in Los Angeles and the founder of Ava M, Skin Five, and The Box by Dr. Ava.

We turned to two hair experts to get the scoop on using protein filler treatments to repair bleached hair. Keep reading for their advice on how and when to use protein filler treatments on bleached hair.

What Is Protein Filler?

Post-bleach damage can be both seen and felt. Hair often appears thinner, and ends are easily split. Running your hands through your hair in the shower even becomes increasingly difficult as bleached hair becomes incredibly stiff when wet. The reduced density and the loss in elasticity are due to injury to the keratin proteins that comprise the hair fiber's inner cortex and the lipids that form the cuticle, meaning that any effective treatment would need to treat both. Luckily, protein filler treatments target the hair keratins our body naturally produces and their cuticle layer.

"Our hair is made of over 90% fibrous keratin protein—a protein found on epithelial cells, which form the center of our hair strand cortex and layers of our hair [nails and skin],"  explains Shamban. Protein filler treatments typically use keratin hydrolysates to treat chemical and environmental damage to the hair. Keratin hydrolysates are usually prepared from keratin-containing animal parts, such as feathers, horns, hoofs, hair, and wool. However, some industries have developed products that use a combination of non-animal sources, such as wheat, corn and soy proteins, to mimic the natural composition of keratin. Protein filler treatments utilize these keratin hydrolysates to help hair recover from the effects of bleaching.

How Do Protein Fillers Work?

After the hair has undergone bleach treatment, the hair cuticle and its pH are affected. According to Shamban, our hair is naturally porous, and the natural pH of hair is around 5.0 for healthy, shiny, bouncy hair. Hair that is balanced has a flat cuticle and keeps in nourishment and moisture, just like a healthy skin barrier. However, when hair is bleached, it becomes too alkaline, which Shamban says causes the cuticle layer to lift and leaves more openings for moisture loss and nutrients that keep hair both strong and healthy.

Shamban explains that a protein treatment introduces keratin hydrolysates that help to restructure the hair strand by restoring its elasticity and strength and improving the hair's overall health and appearance. Neill agrees, adding, "In the process of thermal styling and coloring, often the hair cuticle becomes damaged, frayed, and can flower open. When the cuticle has flowered open, it creates opportunities for damage. Protein fillers go into those flowered cuticles at a microscopic level and fill in the gaps, which strengthens the hair and prevents breakage." Ultimately, protein filler treatments add lipids and proteins to fill the gaps, coat, and add a seal to strengthen the strands, explains Shamban.

It is important to note that keratin is an irreplaceable protein within the hair, meaning that these protein fillers should be considered a treatment, not a cure. Neill compares protein fillers to bandaids - a temporary solution that does not heal the source of the problem. "If you think of a protein filler, it's sort of like a bandaid on a deep wound where you are stopping the blood, but the skin isn't coming back together," Neill explains. "The treatment needs to be ongoing, so every time you go into the salon, you may want to get a treatment or take one at home in-between salon visits," cautions Neill.

The Benefits

Protein filler treatments are a great immediate solution to bleach damage, as they will alleviate many of the problems that arise, including frizz, dryness, and breakage. Both in-salon and at-home protein filler treatments are available, making them accessible at varying price points and concentrations. Protein fillers will immediately go to work filling in the gaps of open hair cuticles and provide the following benefits:

• Strengthens hair: The hair gets damaged through normal wear and tear along with color treatments, explains Neill. He says that protein fillers fill in the gaps within the cuticle, which strengthens the hair strand by reinforcing these weak areas. Shamban agrees, adding that protein gives your hair the building blocks it needs for strength.

• Boosts shine: Dry hair often appears dull due to a lack of moisture. However, when the hair cuticle is disrupted, moisture and other nutrients are lost easily. Shamban shares that protein fillers will seal moisture on hair strands stripped from bleaching, highlights, or harsh color. This added moisture will give hair a major boost in shine.

• Improve elasticity: Brittle hair is more susceptible to breakage from brushing and other mechanical damage. Shamban explains that protein fillers can help to improve elasticity as they replenish and seal in nourishment, which restores vitality and prevents breakage by adding factors to restore elasticity.

• Protect hair from further damage: By filling in the gaps in the cuticle of damaged hair, protein fillers help to protect the hair from further damage - primarily by making the hair stronger and more elastic. While protein fillers cannot repair the damage, they can provide a crutch to the hair that keeps it as healthy as possible in the face of further damage.

• Overall healthier and better-looking hair: Healthy hair is often described as shiny and bouncy. In boosting shine, sealing in moisture, and strengthening strands, protein fillers help improve the hair's overall appearance. Additionally, research has shown that hair treated with hydrolyzed protein has improved hair color and shine.

Who Should Use Them?

According to our experts, many people can benefit from protein fillers. "Anyone with very high porosity hair can benefit from the treatment as they probably have less natural ability to retain and maintain nutrients. People who have recently bleached, colored, highlighted, or otherwise chemically treated hair presumably have considerable damage and can benefit from protein treatments. Even those finding their hair is losing its natural curl and elasticity may also benefit from a protein boost," shares Shamban.

However, it is possible to overdo it with protein filler, which has several consequences. Neill says it's important to know that oversaturating the hair with protein can make it brittle. "Too much protein from using too many protein filler treatments will oversaturate the cuticle and lead to even more breakage. It's a delicate balance that you would want to be prescribed by your stylist."

He says protein fillers are great for people with mild to moderate hair stress from everyday styling and coloring. However, he notes that if you are a serious bleacher and have really put your hair through the wringer, protein fillers may not be enough, and you may want to consider bond-building treatments.

How to Use Protein Filler Treatments on Bleached Hair

Protein filler treatments can be done at home or in a salon. Since protein fillers solve the symptoms instead of the source of the problem, regular treatments are needed to maintain the benefits. Neill recommends consulting a stylist before beginning protein treatments to avoid further damage. "I would always listen to a stylist's recommendation since putting too much protein in the hair is possible, which can also cause breakage." Neill advises doing a protein filler treatment once a week or once every other week.

Shamban agrees, "Either home or office is appropriate for a protein treatment. They can be done easily enough at home in 30 minutes or so. An overnight treatment restructuring mask can also be left in the hair for those who need a little 'extra.'" She recommends looking for products that contain pea protein, amino acids, quinoa, and jojoba.

When applying a protein filler treatment, Shamban recommends the following:

1. Start with clean, damp hair.

2. Then, apply the treatment mask from the scalp to the tip.

3. Comb through the hair to evenly distribute the product, but do not brush.

4. After pulling hair into a bun, wrap it with a microfiber bun or cover it with a shower cap, as this promotes the best absorption and penetration.

5. Leave the treatment on for the recommended time found in the product's instructions.

6. Wash and style.

The Takeaway

Protein filler treatments offer tremendous benefits to hair damaged by bleaching or other environmental stressors. Protein fillers can give bleached hair much-needed strength and shine to protect against further damage. However, it's important to note they cannot fully repair the natural keratin. A stylist should be consulted before beginning protein filler treatments, as too much protein can make hair brittle and cause further damage.

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