Which is best, protein or keratin? Your complete guide

December 12, 2025 •

4 min read

Hair is composed primarily of a structural protein called keratin. The best choice between a protein or keratin treatment depends entirely on your hair's specific concerns, whether it's strengthening weak strands or smoothing frizz for a shiny finish.

Quick Summary

This article explains the differences between protein and keratin hair treatments. It outlines how protein treatments repair and strengthen hair from within, while keratin treatments focus on surface-level smoothing to reduce frizz. The guide helps you choose the right treatment based on your hair type and goals.

Key Points

Protein for Strength, Keratin for Smoothness: A protein treatment rebuilds and strengthens damaged hair from the inside, while a keratin treatment focuses on surface-level smoothing to eliminate frizz.
Assess Hair Needs, Not Trends: Your choice should be based on your hair's primary issue. If it's weak and brittle, choose protein. If it's frizzy and dull, choose keratin.
Consider the 'Stretch Test': To check for a protein deficiency, gently stretch a wet strand of hair. If it snaps, it needs a protein treatment to restore elasticity.
Be Aware of Chemical Risks: Some keratin treatments contain formaldehyde, which can be harmful. Always inquire about the ingredients and ensure good ventilation in the salon.
Aftercare is Crucial: Both treatments require proper aftercare, including using sulfate-free products, to prolong results and maintain hair health.
Avoid Overuse: Excessive protein can make hair brittle, while frequent keratin treatments can cause heat damage. Stick to recommended frequency for best results.

Understanding Hair's Natural Protein Structure

To understand whether a protein or keratin treatment is right for you, it's helpful to first know that hair is naturally composed of a structural protein called keratin. This protein is responsible for your hair's shape, strength, and overall texture. However, various factors can cause this natural protein to become depleted and damaged over time. Chemical processing, frequent heat styling, and environmental stressors can create gaps or holes in the hair's protective cuticle layer, leading to weakness, breakage, and frizz. Both protein and keratin treatments aim to address these issues, but they do so with different focuses and methods.

What is a Protein Hair Treatment?

A protein treatment is designed to replenish and repair the hair's structure by adding hydrolyzed proteins directly to the hair shaft. These treatments act like a temporary filler for the gaps and damage in the hair's cuticle. They don't typically straighten hair, but instead focus on improving the hair's core health and resilience.

Benefits of Protein Treatments

Protein treatments offer several benefits for damaged hair:

Restores Strength: They fortify the hair shaft, making weak hair stronger.
Reduces Breakage: Improved strength means hair is less prone to snapping.
Enhances Elasticity: Protein helps restore hair's natural stretchiness.
Improves Texture: Hair becomes healthier and more manageable.
Boosts Moisture Retention: Protein aids hair in holding onto moisture.

The Risk of Protein Overload

While beneficial, too much protein without enough moisture can lead to protein overload, making hair stiff, dry, and brittle. These treatments are most effective when used sparingly on damaged hair.

What is a Keratin Hair Treatment?

A keratin treatment, also known as a Brazilian blowout, is a chemical process that smooths and straightens hair by infusing it with keratin and other chemicals, sealed with heat. It coats the hair shaft, creating a protective, glossy layer.

Benefits of Keratin Treatments

Keratin treatments primarily focus on smoothing and shine:

Controls Frizz: Sealing the cuticle reduces frizz and flyaways.
Smoothes and Straightens: It can loosen curls and make hair straighter.
Adds Intense Shine: The sealed cuticle provides a high-gloss look.
Reduces Styling Time: Increased manageability speeds up styling.
Long-Lasting Results: Professional treatments can last 2-6 months.

Considerations for Keratin Treatments

Some keratin treatments contain formaldehyde, which can be irritating. Proper ventilation is important, or opt for formaldehyde-free options. High heat used during the process can also cause damage if not done correctly.

Protein vs. Keratin: A Side-by-Side Comparison


Feature	Protein Treatment	Keratin Treatment
Primary Goal	Repairs and strengthens damaged, weak hair from within.	Smoothes and straightens hair, reduces frizz from the outside.
Mechanism	Adds hydrolyzed proteins to fill gaps in the hair cuticle.	Coats the hair shaft with a keratin solution, sealed with heat.
Texture Change	Does not dramatically change natural curl pattern; enhances strength and elasticity.	Loosens curls and waves, resulting in a straighter, sleeker texture.
Key Target Issues	Weakness, brittleness, breakage, high porosity.	Frizz, unmanageable hair, dullness, lack of shine.
Duration of Results	Typically lasts 4-6 weeks and requires more frequent applications.	Can last 2-6 months with proper maintenance.
Aftercare	Use sulfate-free products, avoid protein overload.	Use sulfate-free products, avoid washing for a period post-treatment.
Best For	Chemically-treated, heat-damaged, or weak hair needing internal repair.	Frizzy, unruly, curly hair types seeking smoothness and shine.

How to Choose the Right Treatment for Your Hair

Selecting the right treatment depends on your hair's needs and goals. Consider your main concern:

Weakness or lack of elasticity? The 'stretch test' can help. Wet hair that snaps quickly needs protein for internal repair. A protein treatment is best here.
Frizz, dullness, or unmanageability? If smoothing frizz and adding shine is the goal, a keratin treatment provides a polished finish.

Assess your damage level: Protein treatments rebuild chemically damaged hair, while keratin is better for healthy hair with frizz. Also, consider lifestyle and budget. Keratin is a larger investment but lasts longer. At-home protein options are more affordable and frequent.

The Importance of Proper Aftercare

Aftercare is crucial for both treatments to maintain results and hair health. Use sulfate-free products, minimize heat styling, and follow specific post-treatment instructions from a stylist, especially after a keratin treatment. Regular deep conditioning helps maintain balance.

The Verdict: Which is best, protein or keratin?

Neither treatment is universally best; it depends on your specific hair concerns. Protein treatments are ideal for weak, damaged hair needing internal repair. Keratin treatments are best for frizzy, dull hair seeking smoothness and shine. A hair professional might even recommend a combination over time. By understanding your hair's needs, you can make the right choice for beautiful, healthy hair.

For more information on hair structure, consult sources like the National Institutes of Health (NIH).

Frequently Asked Questions

In some cases, a hair professional may recommend combining treatments for optimal results, using protein to build internal strength and keratin to add external smoothness and shine. It's best to consult a stylist first.

A good test is to take a wet strand of hair and stretch it. If it stretches and then breaks, it likely needs protein. Healthy hair will stretch and bounce back to its original state.

Traditional keratin treatments, which often use heat and chemicals like formaldehyde to seal the protein, can potentially damage hair if overused or applied incorrectly. Keratin itself, however, is a natural protein.

The effects of a protein treatment are temporary, typically lasting between 4 to 6 weeks, and require more frequent applications than a keratin treatment.

No, a protein treatment is for strengthening and repairing and will not permanently straighten your hair. It improves the hair's overall health and elasticity without changing its natural texture.

The main goal of a keratin treatment is to smooth the hair, reduce frizz, and increase shine, making it more manageable and often giving it a straighter appearance.

To maintain results from both protein and keratin treatments, you should use sulfate-free shampoos and conditioners. Keratin treatments also require avoiding washing for a few days immediately after the service.

Yes, many at-home protein and keratin products are available. However, professional salon treatments are often more potent and offer longer-lasting results.