If you're part of the curl community then you've probably heard of protein overload. The idea is that too much protein in hair products causes hair to become dry, brittle, stiff and prone to breakage. To fix it you need to restore the "protein-moisture balance" by reducing protein and increasing moisture.

When I looked for the science behind this I couldn't find any. In fact I found the opposite: many studies showing protein makes hair less brittle, not more. So why does "protein overload" seem so real to so many people?

Turns out there are real phenomena behind it. Just not the one people think.

TLDR

"Protein overload" as described online isn't a real thing. But the symptoms people attribute to it are real: stiff, rough, brittle hair. And they have three real causes: buildup, damage, and under-conditioning.

None of these are fixed by avoiding protein. There are thousands of different protein ingredients in hair products and they do not all behave the same way. Avoiding them wholesale guarantees you'll miss products that might actually help you.

What is "protein overload"?

"Protein overload" is the idea that protein in hair products can cause brittle, dry hair that breaks easily. Alongside this idea is the idea that your hair needs to maintain a "protein moisture balance". But there are a lot of problems with these ideas.

For one, the protein overload concept groups together a huge range of ingredients like hydrolyzed proteins, peptides, amino acids and blames them collectively for dry, brittle, rough hair. But peptides and amino acids aren't proteins, they're constituents of proteins, and they behave completely differently. And hydrolyzed proteins vary enormously depending on the source, the degree of hydrolysis, and whether they've been chemically modified ^[31].

On top of that, balancing protein with moisture makes zero sense because protein IS moisture. Protein is a humectant, meaning it can attract and retain moisture ^[25] as a protective film on the hair ^[32]. And many of the products people blame for "protein overload," like coconut oil-heavy treatments, contain little to no protein at all.

The "protein-moisture balance" framework also depends on "moisture" meaning something it doesn't. In cosmetic chemistry, moisturizing and hydrating are marketing terms ^[33]. I was shocked to learn that hair's water content is largely determined by the humidity around us, not by products ^[15]. What people mean when they say moisturized is just: better conditioned. If you want to read more check out my article on the Moisturization Myth.

If protein isn't the problem, what is?

Buildup

This is the closest thing to real "protein overload." Some protein ingredients, particularly those that have been quaternized (modified to carry a positive charge), are designed to cling to the hair shaft. That's what makes them effective conditioners. But ingredients that cling can also build up over time ^[27].

Positively charged proteins can build up in layers on the hair surface

Regular conditioning buildup tends to feel greasy and limp. Protein buildup is different: it can feel stiff and rough. Cosmetic scientist Valerie George of The Beauty Brains podcast has noted that wheat protein in particular tends to form stiff brittle films, and suggests avoiding high-percentage protein treatments ^[29]. Though it's worth noting that the other host, cosmetic chemist Perry Romanowski, disagrees that protein is commonly a problem at the concentrations found in most products ^[34].

Crucially, the buildup causing your rough hair might not even be protein. For example, hard water minerals and cellulose polymers can all cause similar stiffness. Products marketed for "body," "fullness," or "texture" often deposit film-forming ingredients on the hair shaft, protein or otherwise, because that's how they add volume. These body-adding products are also usually lightly conditioning by design, because heavy conditioning weighs hair down and kills volume ^[35]. These are great for some people, like if you have thin fine oily hair, but for others that combination of light conditioning plus film-forming deposits is a reliable recipe for hair that feels rough over time, especially if you're not clarifying regularly.

The fix: Clarify. Also audit your routine for products claiming to add body, fullness, or texture, and be cautious with old-school high-percentage protein treatments. If you have hard water, you should use a clarifying shampoo that is specifically formulated for hard water.

Damage

High porosity hair is damaged hair with a compromised cuticle

Brittle, dry-feeling, easily broken hair... these are common signs of damage. Damage can come from bleaching, chemical processing, heat, UV exposure, friction from pillowcases, even just years of normal wear.

Damaged hair has a compromised cuticle, sometimes called high porosity. The protective fat layer gets stripped away and the hair surface becomes negatively charged. Regular conditioners and oils don't bind well to this surface and mostly rinse out ^[8].

Ironically, some proteins are actually among the better ingredients for damaged hair. Smaller hydrolyzed proteins can penetrate the gaps left by cuticle damage and help reinforce the strand from within ^{[36] [32]}. But these days bond repair products have largely replaced protein treatments as the standard of care for chemically damaged hair.

The fix: If your hair might be damaged, use products clearly formulated for damaged hair. Look for cationic conditioners that are labeled for damaged, color-treated, or chemically processed hair. Consider bond repair if your hair has significant damage. In the case where it's mainly the ends that are damaged, which I call mixed porosity, focus these products on the ends.

You might also look at my post on The Abbey Yung Method, which is designed for damaged hair.

Under-conditioning

Under-conditioning means your hair surface isn't getting enough lubrication, smoothing, and protection. In consumer terminology it's "dry."

Conditioners include lipids, humectants, silicones, fatty alcohols, and cationic agents. These smooth and protect the hair. If your routine is heavy on cleansing and light on conditioning, or if your "conditioning" products are mostly oils that don't bind well to your hair type, you may be under-conditioned regardless of how much protein is or isn't in your products. Also as I noted before many protein-heavy products are on the lighter-conditioning side to maximize volume.

Leaving hair in a rough, dry-feeling state also makes it more vulnerable to damage over time. If your hair consistently feels dry or rough after your routine, that's a signal something needs to change, not something to just tolerate.

The fix: Find conditioning products suited to your hair's damage level and curl type. If heavy products weigh your hair down, there are lighter options: humectant-rich gels, spray leave ins, lighter creams (see my light products guide). Regular hair masks/deep conditioning can also help. If you notice "dry" spots between washes, you might want to add more leave-in or an overnight treatment mask.

How to shop knowing the truth about protein

The front of the label matters

Before you look at the ingredients list, look at the front of the product. Yes, much of this language is just marketing, but it can still tell you a lot about how a product was formulated:

• Body/fullness/volumizing products are lightly conditioning by design and may deposit film-forming ingredients that make hair feel rough over time. Unless otherwise specified these are generally for people with fine or easily weighed-down hair who don't have issues with brittleness or damage.
• Damage/color-treated/processed hair products contain conditioners formulated to actually bind to compromised hair surfaces. These are what damaged hair needs.
• Moisturizing/hydrating is usually code for more conditioning overall, but if you need conditioning and find these products too heavy, check out my light products guide.

Here's an example, all three of these products technically contain "protein" ingredients but they are formulated very differently:

I think it's very unlikely that the coconut milk product would cause anything resembling "protein overload". The bond one might not be conditioning enough for some hair types, so if you're suffering from symptoms of under-conditioning, it would not be a good choice. The full+ purple one is probably a good choice for hair that's oily, soft, and fine, but not a good choice for hair that's dry, rough, and brittle. It would be cool if hair product companies could make it more clear what kind of hair type each product is best for.

The back of the label

If you want to know what proteins are actually in a specific product, use the CurlsBot Protein Checker. It'll flag protein-related ingredients from our database so you can see what you're actually working with.

Keep in mind a few things about this:

• Some plant proteins are labeled as "extracts" like the "chia seed extract" that is used for one product in our database that clearly says it has chia protein
• Peptides and amino acids are the building blocks of proteins, not proteins themselves
• "Hydrolyzed wheat protein" or such doesn't tell you the size of the protein or even what form it's in

That's why I ultimately think the back of the label is more important than the front here.