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Quick Answer
Cysteine hair treatment can cause side effects such as scalp irritation, dryness, and hair breakage. Heat used during the treatment can also make already weak hair more brittle, while some people may notice temporary hair fall. The risk depends on the product used and the condition of your hair and scalp.
Cysteine hair treatments are popular for reducing frizz and making hair easier to manage. However, the chemicals and heat used during the process can affect the hair and scalp, especially if the hair is already dry, weak, or chemically treated.
Understanding the possible cysteine hair treatment side effects can help you decide if the treatment is suitable for your hair.
What Is Cysteine Hair Treatment And How Does It Work?
Cysteine hair treatment is a salon smoothing treatment that uses a cysteine-based formula to make hair smoother and less frizzy. Cysteine is an amino acid naturally found in hair. The treatment uses the formula and heat to change the shape of the treated hair and create a smoother finish.
A standard cysteine session involves a four-step process to coat and smooth the hair shaft:
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Prepare the hair: The stylist cleans the hair to remove product buildup and prepares it for the treatment.
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Apply cysteine formula: The product is spread evenly through small sections of the hair and left for the required processing time.
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Set the finish with heat: The hair is dried and passed through a flat iron to help create the smoother shape.
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Complete the treatment: The hair is rinsed and dried, leaving the treated lengths smoother and easier to manage.
What Are The Common Cysteine Hair Treatment Side Effects?
Cysteine hair treatment can cause scalp irritation, dryness, breakage, and changes in how the hair feels. These effects can be more noticeable when the hair is already dry, weak, or chemically treated. The product used and the heat applied during treatment also affect the risk.
While results vary by hair type, the most commonly reactions after a cysteine treatment include:
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Scalp reaction: The chemicals may cause itching, redness, burning, or mild swelling if they come into contact with the skin.
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Changes after washing: Hair that feels smooth immediately after treatment may feel rougher or drier after a few washes as the effect wears down.
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More snapping during styling: Weak strands may break when brushed, combed, or exposed to repeated heat.
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Increased loose strands: A few extra strands may be noticed after treatment, but continued or heavy hair fall needs further assessment.
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Reaction to fumes: Some formulas can release fumes when heated, which may cause watery eyes, coughing, or throat discomfort.
Keep in Mind: A label that says formaldehyde-free does not rule out scalp irritation. Ask the salon for the full ingredient list before you book. High-heat flat irons can release formaldehyde gas from hidden donors (like methylene glycol), or low-pH acids can cause chemical irritation.
Is The Damage From Cysteine Treatment Permanent?
No, the damage usually isn't permanent. The treatment only changes the hair above your scalp, so new growth keeps its natural texture. Heat damage on the treated lengths stays until you trim it off.
The table below outlines how side effects evolve over time as treated hair strands age and new hair grows in:
|
Time After Treatment |
What You May Notice |
What Is Happening |
|
First 72 hours |
Itching, a tight scalp, flat hair |
Your scalp reacts to the formula and the heat |
|
Weeks 1 to 4 |
Dry ends, some extra shedding |
Heat stress shows up on the lengths |
|
Months 3 to 5 |
Frizz returns at the roots |
New, untreated hair grows in |
|
After 6 months |
Treated and natural sections look different |
Old lengths still carry any heat damage |
When Can Cysteine Treatment Cause Permanent Hair Damage?
Most cysteine treatment damage affects the treated hair, but severe scalp injury can cause lasting damage to the hair follicles. This is uncommon, but it is important to understand the difference between damage to the hair strand and damage to the follicle.
The difference can be understood by where the damage occurs:
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Treated hair lengths: Damaged areas remain affected until the hair grows out or is trimmed.
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New hair growth: Hair that grows after the treatment keeps its natural texture.
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Hair follicles: A properly performed treatment should not damage the follicles.
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Severe scalp injury: Severe chemical burns or persistent scalp inflammation can scar hair follicles (cicatricial alopecia), which may lead to permanent hair loss.
How Can You Reduce Side Effects After The Treatment?
You can reduce the chance of further dryness, breakage, and irritation by keeping your hair care gentle after a cysteine treatment.
Adopting gentle hair care practices protects fragile, heat-stressed hair lengths and prevents excessive shaft breakage:
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Follow the first-wash instructions: Wash your hair only when your stylist or the product instructions recommend.
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Use a mild shampoo: Clean your scalp gently without rubbing the treated lengths too much.
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Condition after washing: Apply conditioner to the mid-lengths and ends to keep them softer and easier to manage.
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Limit heat styling: Avoid frequent straightening and use lower heat when blow-drying.
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Handle wet hair gently: Pat your hair dry and use a wide-tooth comb instead of pulling through tangles.
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Avoid another chemical treatment too soon: Give your hair time before colouring, bleaching, or having another smoothing treatment.
When Should You See A Doctor After Cysteine Treatment?
See a doctor if a reaction gets worse after 48 hours or symptoms are severe, worsen after treatment, or continue instead of improving. Mild, short-lived discomfort may settle, but stronger reactions can indicate a scalp injury or another condition that needs assessment.
Certain post-treatment reactions indicate significant scalp irritation or severe chemical exposure that requires professional medical assessment:
|
Sign |
What To Do |
|
Blisters, oozing or swelling on the scalp or face |
See a dermatologist promptly, as these can indicate a significant skin reaction. |
|
Patchy bald spots |
Arrange a dermatology assessment to identify the underlying cause. |
|
Hair fall that lasts beyond 3 months |
Have your hair and scalp assessed rather than assuming the treatment is responsible. |
|
Severe headaches, nausea, or dizziness following fume exposure during treatment. |
Seek medical care and tell the clinician about the recent smoothing treatment. |
Keeping Your Hair Healthy After Cysteine Treatment
Cysteine treatment can leave the treated hair more prone to dryness or breakage, but gentle aftercare can help protect it as it grows out. New hair will continue to grow with your natural texture, while damaged lengths can be trimmed gradually.
If hair fall, scalp irritation, or breakage continues after the treatment, do not assume the cysteine treatment is the only cause. Persistent symptoms may need a dermatologist's assessment to identify what is affecting your hair and scalp.
Losing more hair than usual since your last salon visit?
Take Traya's Hair Test to understand your pattern before choosing a treatment plan.
FAQs
How many times can hair smoothening be done?
Stylists commonly advise a maximum of 2 sessions a year. On each visit, apply the cream only to new roots. Going over the same lengths again adds to the bond damage.
Does hair grow faster after smoothening?
No. Growth speed comes from your follicles, and the cream never gets to them. Straight hair hangs lower than wavy hair, so it can just look longer.
Which is better for my hair, hair smoothening or hair straightening?
For most hair, smoothening is the gentler option. Permanent hair straightening breaks more bonds and causes more breakage. Both still leave treated lengths weaker than untreated hair.
References
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Barreto, T., Weffort, F., Frattini, S., Pinto, G., Damasco, P. and Melo, D., 2021. Straight to the point: what do we know so far on hair straightening?. Skin Appendage Disorders, 7(4), pp.265-271. https://doi.org/10.1159/000514367
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Dias, M.F.R.G., 2015. Hair cosmetics: an overview. International journal of trichology, 7(1), p.2. https://doi.org/10.4103/0974-7753.153450
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Lee, Y., Kim, Y.D., Hyun, H.J., Pi, L.Q., Jin, X. and Lee, W.S., 2011. Hair shaft damage from heat and drying time of hair dryer. Annals of dermatology, 23(4), pp.455-462.. https://doi.org/10.5021/ad.2011.23.4.455
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U.S. Food and Drug Administration. (2021, March 2). Formaldehyde in hair smoothing products: What you should know. https://www.fda.gov/consumers/consumer-updates/formaldehyde-hair-smoothing-products-what-you-should-know
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