If you have ever stared at a shelf full of “bond repair” products and wondered why everything suddenly claims to fix your hair’s internal structure? Well, you are not alone. I researched so-called "bond repair" products for months to write this guide.

What I uncovered is that not all bond repair products are alike. Some target the strong internal bonds that actually matter for curl integrity. Others build weak, temporary bonds using ingredients that are common in just regular conditioners. And the labels rarely help you figure out which is which.

So this guide is here to cut through the noise. If your hair is damaged, fragile, high porosity, or just not behaving the way it used to, I want to help you understand which products can genuinely make a difference and which ones are mostly buzzwords. By the end, you’ll know what type of bond repair your hair actually needs, when it is worth investing in stronger systems, and when a well formulated drugstore product will do the job just as well.

TLDR

There are two major types of bond repair products: strong and weak. They do not work the same way.

There are only FOUR major strong bond repair products: Olaplex, Epres, k18, and Living Proof Triple Bond Complex. And they are pretty expensive.

These strong bond repair products target COVALENT bonds like Disulfide bonds, which are strong bonds that are really only broken in two situations

• Chemical processing (bleaching, perming, relaxing, keratin treatments, etc.)
• Extreme heat damage

If you don't have those specific types of damage, you really don't need strong bond repair products.

But if you do, the best use of them is DURING chemical treatments at the salon, using the professional versions of Olaplex or k18.

At home I'd prioritize Olaplex OR Epres (they have similar mechanisms) over the other choices. But if you're REALLY into mitigating damage you can add on k18 AND/OR Living Proof Triple Bond Complex since they work differently.

Epres Bond Repair Treatment

My choice for strong bond repair

Buy at EpresBuy on Amazon

Always prioritize the treatments. The matching shampoos, conditioners, leave-ins etc. have less of the active. They may help but the evidence is sketchy.

If your hair is high porosity (find your porosity type here), from everyday wear and tear or from lighter chemical services like highlights or box dye, the weak bond builders might help, but most of them are basically well formulated conditioners with trendy language. They might not work any better than the "repair" deep conditioner you already use.

But if you want to try them out, my top weak bond picks are:

Garnier Fructis Hair Filler Inner Fiber Repair Pre-Shampoo Treatment

A great weaker bond repair product that also could work to treat hard water buildup

Buy at CVSBuy on Amazon

Pantene Pro-Vitamin Essence Weightless Leave-On Treatment

I would recommend this or ANY of the Pantene Miracle Rescue line as well, for both bond repair and general conditioning

Buy on Amazon

Both have good science behind them, work well, and are affordable.

In the end don't think of bond repair as an essential part of hair care routines. Other conditioning products can provide similar results.

What Are Bond Repair Products?

Well, there is no regulation or standardized definition but Dr. Paul Corwell of the Tri-Princeton Institute and Dr. Jennifer Marsh are two experts who have proposed defining it as product with ingredients that penetrate into the cortex, improves or restores its internal structure, and enhances mechanical properties ^[10]. That is the definition I'm going to use because if we just counted anything that creates any bonds anywhere, I'd have to include basically every conditioner on the market.

Penetration is actually not easy to do, even in damaged hair where the cuticle has cracks. Even an impaired cuticle provides an obstacle to ingredients getting in. Chemists have come up with ways to get around this like making the active smaller and altering its charge.

For structural changes in the cortex this can be really hard to prove and well, expensive. Since there are no consequences for making inaccurate claims about bonding, it's no surprise that most brands don't bother.

With "enhancing mechanical properties" that means increasing the hair's strength, resistance to heat, and flexibility. But remember it's also something a lot of conventional conditioners do.

Strong Bond Repair Products

Strong bond repair products target covalent disulfide bonds. These bonds:

• Hold the structure of the hair cortex together
• Give curls their shape (the curlier your hair is, the more of these bonds you have ^[11])
• Are very strong
• Are only broken by strong chemical processes (bleaching, coloring, perming, relaxing, keratin treatments, etc.) or extreme heat

When these break, your curl structure can be damaged.

There are ONLY four major products available to consumers that claim to repair strong, covalent bonds:

The Big Four

Olaplex

The original product of this type, has the most independent peer-reviewed studies but that's not much. Most claims are based on using 3-4 products together which gets expensive. Active: Bis-Aminopropyl Diglycol Dimaleate

Buy at OlaplexBuy on Amazon

Epres

The same chemist behind Olaplex, should kind of work similarly, and for the sole reason it is JUST ONE PRODUCT I strongly prefer it to Olaplex. Less complexity will save you time and money. Active: Diethylhexyl Maleate

Buy at EpresBuy on Amazon

K18 Molecular Repair Hair Mask

This claims to not only reconnect the disulfide bonds, but also to repair the structure of the keratin itself through another type of covalent bond, the peptide bond. In the one peer-reviewed study where it was tested against Olaplex, it did not perform as well but it also worked in very different way. Active: sh-Oligopeptide-78

Buy at K18Buy on AmazonBuy at Sephora

Living Proof Triple Bond Complex

This one is kind of a mystery to me. There are some papers about bond repair using the same active but in a very different process. The active system centers around isopentyldiol, though the exact mechanism is not clear. Active: Isopentyldiol

Buy at Living ProofBuy on AmazonBuy at Sephora

Do they really repair disulfide bonds

One of the major problems with these "bond repair" products is that the evidence supporting their claims is weak. That's why you're not going to find any diagrams in this post like you might see elsewhere. Those diagrams probably aren't correct.

Because these products are based on patented trade secrets it's hard to learn how they actually work. I had to base my research on their patents, two independent peer reviewed studies (one with both k18 and Olaplex, one with just Olaplex)^[12][13], and some papers describing similar systems in the case of Living Proof's product^[14].

None of the independent studies found proof that these products rebuild disulfide bonds directly. That part of the marketing appears to be wishful thinking. But the research does show evidence of other covalent bonds forming, which is still meaningful because covalent bonds are the strongest bonds you can put in hair.

So they are doing something, it's just not what the cute diagrams on the brands’ blogs suggest. These diagrams typically show "cross linking" which is connecting the end of one broken cysteine residue to another, forming a connection. When in reality it seems like for Olaplex at least that it's just capping the ends of the broken bonds, which is useful but not what the diagrams suggest. k18 the one study it was in didn't really show it doing anything on the cortex, it seemed to be more of a conditioner.

When to Use Strong Bond Builders

Reading the patents I was interested in how many of them described systems used DURING chemical processing (like bleaching) of hair rather than afterwards.

If these products are capable of repairing disulfide bonds, it's most likely this would occur during or shortly after chemical processing.

This is the window where the internal structure is disrupted and ingredients can interact with reactive sites in the hair. Once the hair is already damaged and stabilized, the effect is weaker.

So my top recommendation would be if you're heavily processing your hair at a salon, have your stylist include one of the strong bond building products! I'd pick Olaplex or Epres personally. This can make a massive difference for extreme types of processing like bleaching dark hair into very light colors.

Post processing or if you do processing at home, the at-home treatments may help but not as dramatically.

The new Olaplex for curls

Olaplex released a curl-focused system called Bond Shaper that uses a peptide called Oligopeptide-300. There is almost no publicly available technical info and it's only available for professional stylist use in salons.

The Olaplex Bond Shaper gel contains the standard Olaplex active (Bis-Aminopropyl Diglycol Dimaleate) and not the new peptide.

I wish I knew more about the science of these products but there is little info on either the new active Oligopeptide-300 or on whether the old active Bis-Aminopropyl Diglycol Dimaleate would be helpful in a gel.

Are these protein treatments?

Olaplex, Epres, and Living Proof Triple Bond have no protein or protein derivatives in them.

k18 is based on a peptide. Amino acids make up peptides, and peptides make up proteins.

Proteins derivatives like peptides are extremely diverse and I don't see any plausible reason they could cause the so-called "protein overload" condition (which is likely just buildup, see my post on the subject)

k18 also DOES have Hydrolyzed Wheat Protein in it, which is a protein people commonly complain about making their hair feel stiffer.

Can you use multiple bond repair products together?

Yes, as there are 3 different systems here so the only ones I wouldn't use together are Epres and Olaplex which use the same type of Maleate-based system. So

1. Epres OR Olaplex
2. k18
3. Living Proof Triple Bond

and of course probably as many of the weak bond repair products as you want, which I'll cover next.

Weak Bond Repair Products

Weak bond repair products do not claim to repair stronger bonds, but merely to add new bonds. These bonds:

• Are weaker (hydrogen and ionic bonds)
• More temporary
• But still could help improve hair's condition and prevent further damage by improving its structural integrity

There is sadly no real evidence these are better than regular conditioners but some of them are quite good as conditioners.

Common Weak Bond Repair Actives

Earlier I defined bond repair ingredients as those that penetrate into the cortex, improve or restore its internal structure, and enhances mechanical properties. Under this definition there are many active ingredients that qualify but the major groupings I see are:

• Acids
  • Citric Acid (best evidence)^[15]
  • Gluconic Acid: Hydroxypropyl Gluconamide on ingredient lists, promising with some theoretical and practical evidence, including the ability to temporarily mend split ends^[16][17]
• Protein derivatives which are a hugely diverse group of ingredients with varying levels of evidence behind them, and different properties based on their MW (molecular weight)^[18]
  • hydrolyzed proteins like hydrolyzed keratin
  • peptides
  • amino acids like arginine, serine, and valine
• Vitamins like Panthenol^[19]

The best weak bond repair actives to look for

Citric Acid

Of acids my favorite is Citric Acid, a common ingredient that does double duty, both creating internal bonds and chelating hard water minerals, which can make a major difference in how hair looks and feels. A recent paper shows evidence that it penetrates, improves the structure of hair, and enhances its strength ^[15].

Panthenol

Of vitamins probably the star is panthenol which was also the subject of a recent paper that showed it penetrating into the cortex, creating bonds inside it, and improving hair's strength ^[19]. Panthenol is also just a really good conditioner.

Hydrolyzed Keratin

One of the few actives specifically tested on curly hair. In a study it found that different weights of hydrolyzed keratin helped prevent breakage in relaxed very curly/coily hair ^[18].

Recommendations

For cost, availability, and science, my top picks are:

Recommended Products

Garnier Fructis Hair Filler Inner Fiber Repair Pre-Shampoo Treatment

A great weaker bond repair product that also could work to treat hard water buildup. Actives are citric acid and and a VERY small amount of a protein derivative.

Buy at CVSBuy on Amazon

Pantene Pro-Vitamin Essence Weightless Leave-On Treatment

I would recommend this or ANY of the Pantene Miracle Rescue line as well, for both bond repair and general conditioning. Panthenol is the main active in all of them. The Miracle Rescue line also has Keratin but this just has the amino acid histidine.

Buy on Amazon

These work well for high porosity hair with mild to moderate damage without charging luxury prices. Plus they are just good products in general! The Garnier can also function as a hard water treatment if that's something you're dealing with (see my guide on hard water).

Special Curl Focused Bond Repair Products

There are a bunch of curl-specific bond products out there now but it's unclear what makes them better for curls than non-curl bond repair products as they mostly have the same actives. Many of them claim to have third party testing but then don't specify what type of hair they tested on. I wish more brands would be transparent about how they tested their products. Like were they tested specifically on curly hair? How did the results compare to non-curl bond repair products?

Common Bond Repair Products

Here is a table so you can compare some common bond products

Treatments vs Other Products

Many brands now have entire lines of bond repair products from pre-shampoo to stylers. The most important products are the treatments, which have the highest amount of the active ingredients.

But some of these have been designed as part of a system. When researching them you should look to see what the claims are for. Like for the Shea Moisture bond products it says the internal tests used their "4 step system", so the claims are for the system of products used together, not just single products. Though weirdly the claims say it was just compared to non-conditioning shampoo...which is not impressive. A better test would be to test against similar 4-step systems without the bonding actives.

For the actives in Dove and other Unilever products, there are some tests mentioned in the patent that say that the shampoo and conditioner do have an effect on hair strength, and the effect increases the more you use them.

So there isn’t much evidence that these are beneficial, but theoretically they could be.

The Abbey Yung Hack

Hair influencer Abbey Yung (see my guide to her method) noticed something odd. Some bond repair treatments tell you to use them before shampoo and others say after shampoo but before conditioner. So she asked the manufacturers directly. Most told her the same thing: these treatments are generally more effective after shampoo, when the hair is clean and the active ingredients can reach the cortex more easily.

If you want to get the most out of a bond repair treatment, using it after shampoo is the better bet.

That said, many of these products need to sit for five minutes or more. Most people do not want to stand in the shower freezing while the clock runs. This is probably why some brands default to pre-poo instructions. It is less effective but more convenient.

Can bond repair damage hair?

I have seen people complain about almost every single one of these products online, even the non-protein derived ones saying their hair was ruined.

There have been lawsuits alleging hair loss linked to Olaplex, though causation hasn’t been proven. The Beauty Brains, a podcast hosted by two cosmetic chemists, said on Episode 329 that they were skeptical that some of the ingredients the lawsuit blamed could do that type of damage.

As they say hair loss is very complex, can have so many causes. And these products are often used by people with very damaged hair. Sometimes very damaged hair just can't be saved. Or they think they can use more damaging stuff because the bond builders protect them.

Like most hair loss lawsuits, we will likely never know the answer because they are settled out of court.

Are these products really any better than regular "hair repair" conditioning products?

That is the question I always ask. For example, one peer-reviewed study of Olaplex found it increased tensile strength 47.6% ^[12].

That sounds impressive until you realize that A LOT of other cheaper actives have at least some science that shows they can also increase tensile strength like one study showed a coconut-based oil increased tensile strength by 36% ^[20].

I see many people lamenting they can't afford the more expensive strong bond builders and worrying they are missing out on something truly revolutionary. I'm not sure they are! I really want to see studies testing "bond repair" actives against other conditioners.

Another thing I can't stress enough is that so much of the research is on EXTREMELY damaged hair OR hair that's in the process of being bleached/permed/relaxed. We don't have a ton of info about how well these work as at-home treatments on less damaged hair.

Overall there is just a real shortage of peer-reviewed research on these products especially on curly hair. Peer-review isn't perfect, but it helps us get more of an idea of how and why these products work, which can help us choose the right products for our problems.

Can you benefit from bonding products if your hair is low porosity (undamaged)

There isn't any research on this so I can only speak to personal experience, which is that I've tried several protein-based "bond repair" products on my short undamaged hair and they really didn't seem to do much. But some people report that these treatments boost their curls/waves. I'd like to see more study on this. And in the meantime I'm not sure I'd seek out these products with the hope that they'll boost curls/waves in your undamaged hair.

I also tried out the two recommended weak bond repair products. The Garnier Hair Filler treatment worked well because I have very hard water, and it contains citric acid, which helps chelate that (remove hard water deposits see my guide to hard water). I'm always looking for good hard water treatments to recommend to people so I'll probably keep using this one and update my hard water guide to include it.

The Pantene gold line (Miracle Rescue) in general has been beneficial for my hair, even if it doesn't need bond repair. These are just quality products. Panthenol isn't just a "bond repair" ingredient, it also can help soften coarse white hairs that I've gotten with age to make them more manageable.

So I wouldn't specially seek out bond repair for my low porosity hair, but I also wouldn't rule out products just because they are labeled as "bond repair".

Final Thoughts

The strong systems are the only genuinely new science here, and even those have limits. The weak systems are often just common ingredient rebranded as "bond repair".

The most important thing is not buying all the claims that bond repair products make and viewing bond repair as not something magical, but just another type of conditioning.

Further resources

• Evaluating Bond Repair Claims, a talk that Dr. Jennifer Marsh did for The Beauty Claims E-summit
• How bond builders repair hair: A more technical article, you may need to sign up for an account to read it
• The Skincare Bookshelf on Instagram has a series of posts on bond repair that are very technical and helpful for understanding the science behind these products

About the Author

Melissa McEwen is the creator of CurlsBot. She is a software developer with training in science writing and a B.S. in Agricultural Science. Her writing has appeared in publications such as NPR and Quartz.