A 55-year-old woman's teeth were whitened with a 35% hydrogen peroxide product. In the European Union, no tooth-whitening product sold as a cosmetic may contain more than 6%, and even that strength is reserved for dentists. Her doctors now suspect the whitening solution caused an airway blockage that collapsed part of her lung and looked like a tumor on her scans.
The case, published in Cureus in January 2026 by Redouene Sid Ahmed Benazzouz, Massinissa Benyagoub and Nassim Nedjar of Laghouat Public Hospital in Algeria, describes a North African cook and lifelong nonsmoker with no history of lung disease. Their report proposes that she inhaled vapors or tiny droplets of the whitening solution during the procedure.
The strength of that product is what gives the story reach beyond one patient. A 35% concentration is far above Europe's ceiling, yet it falls within the range of strong gels used in many dental offices elsewhere, including the United States.
Three Months of Coughing Before the Bleeding Started
Symptoms began shortly after the whitening procedure, which the authors say was "complicated by intense pharyngeal pain, ulcerative lesions, and severe coughing." A dry cough followed her for three months. After a smaller episode of coughing up blood, she had a massive bleed that sent her to the hospital, along with shortness of breath at rest.
A chest CT showed "complete left lower lobe atelectasis," meaning the lower part of her left lung had collapsed. The cause was a soft-tissue lesion plugging the airway, the kind of finding that usually starts a search for cancer. Blood counts, inflammation markers, and clotting tests were normal.
Doctors attempted a bronchoscopy, but stopped because her oxygen dropped, her coughing continued and her blood pressure spiked. Instead of a solid mass, they saw thick mucus clogging the airway. Shortly afterward, she coughed up a large amount of thick mucus and began to improve. Bacterial and tuberculosis cultures came back negative.
About four months after her symptoms began, a follow-up CT showed that the lesion was gone and her lung had fully re-expanded, with only minor signs of scarring.
One detail stands out. The whitening exposure "was not initially disclosed," the authors wrote, and came to light only later. Once it did, it offered an explanation that imaging alone had not.
Europe Caps Whitening Products at 6%. This One Was 35%
Under Council Directive 2011/84/EU, whitening products sold directly to consumers in the EU may contain no more than 0.1% hydrogen peroxide. Products above 0.1% and up to 6% may be sold only to dental practitioners. The first use in each treatment cycle must be done by a dentist or under direct supervision, and the products may not be used on anyone under 18.
Those limits now sit in the EU's main cosmetics law. Ireland's health products regulator states plainly that whitening products above 6% are prohibited and considered illegal cosmetic products.
The 35% product in this case was nearly six times that ceiling. Algeria is not an EU member, and the report does not say where the procedure took place or who performed it, so it does not suggest that any local rule was broken.
The United States draws the line differently. The American Dental Association describes in-office "power bleaching" as using "concentrated solutions of hydrogen peroxide in water," with or without light activation, applied for up to 30 minutes. An ADA News overview puts those in-office concentrations at 15% to 43%. The ADA also notes that professional whitening products are not eligible for its Seal of Acceptance, a voluntary program for certain over-the-counter products.
The Safeguards Meant to Keep Peroxide Out of Your Airway
For most people, in-office whitening causes only mild problems. According to the ADA, temporary tooth sensitivity and gum inflammation are the most common side effects. Lung injury is not a recognized risk of properly performed whitening, and a single case report cannot show that it is.
Concentrated peroxide is a known irritant, however. The federal Agency for Toxic Substances and Disease Registry warns that inhaling vapors from concentrated solutions, those above 10%, "may result in severe pulmonary irritation."
That is why dental offices use a protective barrier over the gums. The ADA's guidance cites research suggesting that local anesthesia be avoided during in-office bleaching "so that patients can detect any burning sensations, which could indicate gel seepage through the barrier." In effect, the patient's own sense of burning serves as an early warning.
The woman in this case had intense throat pain and severe coughing tied to the procedure, a sign that the solution may have reached well beyond her teeth.
For patients, the lesson is modest but practical. Burning in the throat, coughing, or trouble breathing during whitening is not something to push through. Telling the dental team right away lets them stop, rinse, and check the barrier. Anyone with a lasting cough, blood in their sputum, or breathing trouble after a dental procedure should see a doctor and mention the treatment.
The case also has limits. No tissue or cytology testing was done on the material she coughed up, which the authors acknowledge "limits diagnostic certainty." Their search of the medical literature found no earlier reports of a tumor-like airway blockage like this one, so the link to peroxide remains their best explanation rather than a proven cause.
Key Questions Answered
What happened to the woman in this case?
A 55-year-old woman developed a lasting cough after a dental whitening procedure using 35% hydrogen peroxide. About three months later, she coughed up a large amount of blood, and scans showed part of her left lung had collapsed behind a tumor-like lesion.
Did she have lung cancer?
No cancer was found. A bronchoscopy showed thick mucus rather than a solid mass; she coughed up the mucus soon afterward, and a later CT showed her lung had fully re-expanded.
How does 35% compare with European limits?
It is nearly six times the EU maximum. Whitening products above 0.1% hydrogen peroxide may be sold only to dentists in the EU, and products above 6% are not allowed as cosmetics.
Are gels this strong used in the United States?
Yes. ADA News reports that in-office whitening uses hydrogen peroxide concentrations of 15% to 43%.
Is professional teeth whitening dangerous?
For most people, the ADA says the most common side effects are temporary tooth sensitivity and gum inflammation. This is a single case report, and it does not show that lung injury is a common risk.
What should patients do if something feels wrong during whitening?
Tell the dental team right away about burning in the mouth or throat, coughing or trouble breathing, so they can stop and check the gum barrier.
Published by Medicaldaily.com
