Protein & Keratin Hair Treatment

What it is

Hair fibers are made largely of keratin proteins. Bleaching, chemical processing, heat, ultraviolet exposure and everyday wear can alter the cuticle and internal structure of the hair shaft, contributing to roughness, porosity and breakage.

Protein treatments are conditioning treatments containing proteins, hydrolyzed proteins, peptides or amino acids. Depending on their molecular size and formulation, these ingredients may deposit on the hair surface or penetrate to some degree into damaged hair. Their effects are cosmetic and physical, rather than biological repair of a living structure.

Keratin smoothing treatments are a different category. They are salon services designed primarily to reduce frizz, alter curl or make hair easier to straighten and style. A smoothing solution is applied to the hair and is commonly followed by heat treatment with a blow dryer and flat iron.

Despite the shared word "keratin," a protein-conditioning treatment and a keratin smoothing service should not be assumed to work in the same way.

Why people consider it

• Hair that has become rough, porous or prone to breakage after bleaching or other chemical processing
• Wanting temporary conditioning or improvement in the feel and manageability of damaged hair
• Frizz or curl that someone wants to reduce with a smoothing treatment
• Wanting hair that is temporarily easier to straighten or style

What the experience is like

Protein treatment: a protein-containing conditioning product is applied to the hair. Depending on the formulation, it may be left on for a period of time, used with heat, rinsed out or incorporated into another conditioning service.

Keratin smoothing: a smoothing formulation is applied through the hair and is commonly followed by blow-drying and flat-ironing. Heating is an important safety consideration because some smoothing products can release formaldehyde gas during this stage.

Application time, heat settings, washing instructions and how long the result lasts depend on the particular product and protocol. Follow the instructions for the specific formulation rather than assuming that all protein or keratin treatments require the same aftercare.

Limitations & considerations

• Protein treatments do not permanently reconstruct damaged hair. Hair fibers are non-living structures, and cosmetic products can modify their surface or physical properties without restoring them to an undamaged biological state
• The behavior of hydrolyzed proteins depends partly on molecular size and formulation. Evidence for one hydrolyzed keratin preparation should not automatically be transferred to every protein treatment
• Laboratory studies showing changes in penetration, stiffness or breakage of treated hair fibers do not establish how much visible benefit a particular salon treatment will provide
• Keratin smoothing is primarily a smoothing and manageability service. It should not be confused with a treatment for hair loss, scalp disease or follicle function
• Some smoothing products can release formaldehyde when heated. Exposure can affect both the person receiving the service and salon workers, particularly when ventilation is inadequate
• Labels such as "keratin," "Brazilian," "protein," or "formaldehyde-free" do not by themselves describe the complete chemistry or safety profile of a smoothing product. Ask for the product name and ingredient or safety information when available
• Repeated chemical processing and high-temperature styling can themselves affect the hair shaft, so the condition of the hair and the specific procedure matter when considering another treatment
• Results and longevity vary by formulation, hair condition, washing, styling and other hair-care practices