Hair straightening treatments are often presented as harmless beauty upgrades, smoother strands, less frizz, and long-lasting shine. However, recent hospital data from Israel tells a far more serious story. Despite an official ban, dozens of women and teenage girls have been hospitalized with acute kidney failure after exposure to glyoxylic acid, a chemical still used in certain hair straightening products.
From a pharmacist’s perspective, this raises an urgent public health question, how can a cosmetic product applied to the scalp end up damaging the kidneys? To understand this, we need to look closely at the chemistry, the biology, and the way these products are used.
What Is Glyoxylic Acid?
Glyoxylic acid is a small organic acid involved in normal amino acid metabolism. In theory, this may sound harmless. In practice, its behavior changes dramatically depending on where and how it is used.
In cosmetics, glyoxylic acid is added to some hair straightening treatments because it can temporarily alter keratin bonds, the protein structures that determine whether hair is curly or straight.
At this point, it’s important to clarify a common source of confusion. Glyoxylic acid is not the same as glycolic acid. While glycolic acid is a well-known alpha hydroxy acid safely used in skincare at controlled concentrations, glyoxylic acid follows a very different metabolic pathway in the body.
This distinction is critical, and often overlooked in marketing.
Why Is Glyoxylic Acid Used in Hair Straightening Products?
Manufacturers favor glyoxylic acid because it offers strong straightening effects without formaldehyde. As a result, these products are frequently advertised as “safer” or “formaldehyde-free.”
Formaldehyde free does not always mean safe.
Unlike facial skincare, hair straightening products,
• Use higher concentrations
• Remain on the scalp for longer periods
• Are activated with high heat
As a result, the risk becomes much higher.
How Does the Chemical Enter the Body?
Under normal circumstances, the skin acts as a protective barrier. However, during hair straightening treatments, several factors weaken this defense.
• First, the scalp is naturally porous and highly vascular.
• Second, flat irons generate intense heat.
• Third, many users experience scalp irritation or micro burns.
Taken together, these conditions allow glyoxylic acid to pass through the scalp and enter the bloodstream. Once that happens, the exposure is no longer cosmetic, it becomes systemic.
What Happens After Absorption?
Once inside the body, glyoxylic acid does not remain unchanged. Instead, the body rapidly metabolizes it.
This is the main problem.
Glyoxylic acid is converted into oxalate
Oxalate is normally eliminated by the kidneys in small amounts. However, when oxalate levels rise suddenly, the kidneys can become overwhelmed.
How Oxalate Triggers Kidney Failure
Excess oxalate binds with calcium to form sharp microscopic crystals. Over time, or even within hours, these crystals lodge inside kidney tubules.
As a result,
• Urine flow becomes obstructed
• Inflammation rapidly increases
• Kidney tissue is directly injured
This process explains why patients developed acute kidney injury (AKI) so quickly after hair treatments.
Clinical Evidence from Israel
Importantly, this is not a theoretical risk.
A landmark study published in the American Journal of Kidney Diseases documented dozens of real-world cases. Since 2023, at least 38 women and teenage girls were hospitalized after hair straightening treatments containing glyoxylic acid.
Importantly,
• Ages ranged from 14 to 58
• None had pre-existing kidney disease
• All had scalp irritation
• Several required dialysis
• Symptoms appeared within hours
This was the first study worldwide to formally establish this connection.
Why Are Cases Still Occurring Despite Safety Concerns?
Even when certain hair straightening products are restricted or regulated in some places, cases of harm continue to appear. This happens because,
• Products are still easily purchased online.
• Imports come from countries with weaker safety regulations.
• Some products are mislabeled or don’t clearly list harmful ingredients.
• Consumers may not recognize dangerous chemicals in ingredient lists.
In short, regulation alone is not enough, consumer awareness and caution are essential everywhere.
Early Warning Signs After Hair Straightening
Because kidney injury can develop rapidly, recognizing symptoms early is essential. Within hours, patients may experience,
• Sudden nausea or vomiting
• Severe headache or dizziness
• Reduced urination
• Pain or burning while urinating
• Scalp rash or burning
At this stage, prompt medical care can prevent permanent damage.
Can This Lead to Chronic Kidney Disease?
So far, most patients recovered fully. Even so, nephrologists warn that severe acute injury can leave lasting scars.
In addition,
• Repeated exposure increases risk
• Some individuals may have genetic susceptibility
• Research into long term outcomes is ongoing
From a pharmacist’s viewpoint, this is deeply concerning, especially because the affected individuals were otherwise healthy.
The Real Cost of Beauty
An old saying suggests that beauty requires sacrifice. Medicine strongly disagrees.
Hair texture is a cosmetic preference. Kidney failure is a life altering medical condition.
No hairstyle is worth hospitalization, dialysis, or permanent kidney damage.
Pharmacist’s Takeaway
In short,
• Glyoxylic acid can behave like a drug once absorbed
• Heat dramatically increases toxicity risk
• Scalp exposure turns a cosmetic into a systemic hazard
• Awareness saves lives
Healthy beauty should never compromise internal health.
FAQs
Q1. What is glyoxylic acid and why is it used in hair straightening products?
Glyoxylic acid is an organic acid used in some hair straightening treatments because it temporarily alters keratin bonds, allowing hair to appear straighter when heat is applied. It is often marketed as a “formaldehyde-free” alternative.
Q2. Is glyoxylic acid the same as glycolic acid used in skincare?
No, Glyoxylic acid and glycolic acid are chemically and biologically different. Glycolic acid is an alpha hydroxy acid commonly used in skincare at safe concentrations, while glyoxylic acid can be converted into harmful oxalate when absorbed into the bloodstream.
Q3. How can a hair product cause kidney failure?
During hair straightening, high heat and direct scalp contact allow glyoxylic acid to penetrate the skin. Once absorbed, the body converts it into oxalate, which can rapidly damage kidney tubules and trigger acute kidney injury.
Q4. What symptoms have been reported after glyoxylic acid hair treatments?
Reported symptoms include sudden nausea, vomiting, dizziness, severe headache, abdominal pain, scalp irritation, reduced urination, and pain during urination. Symptoms typically appear within hours of the treatment.
Q5. Who is at risk of kidney injury from these treatments?
Women and teenage girls aged 14 to 58 with no prior kidney disease have been affected. This indicates that even healthy individuals can be at risk, particularly when products are heated and applied close to the scalp.
Q6. Can kidney damage from these treatments become permanent?
Most patients recovered after hospitalization, but severe acute kidney injury can increase the risk of long-term kidney problems. Ongoing research is exploring whether genetic susceptibility plays a role.
Q7. What warning signs should prompt immediate medical attention?
Sudden vomiting, nausea, dizziness, reduced or painful urination, or scalp burns following hair straightening should be treated as medical emergencies to prevent lasting kidney damage.
Q8. What is the safest approach to hair straightening from a health perspective?
Avoid products containing glyoxylic acid, do not apply chemical straighteners directly to the scalp, and avoid unregulated or online products. Cosmetic treatments should never compromise kidney health.
Disclaimer
This content is for educational purposes only and does not replace professional medical advice.
Call to Action
Before any hair treatment, read ingredient labels carefully, avoid unapproved products, and prioritize safety over trends.
References
• American Journal of Kidney Diseases, Clinical evidence linking glyoxylic acid hair treatments to acute kidney injury
• The Times of Israel, Expert reporting from Shaare Zedek and Rabin Medical Centers