Carboxymethylcellulose allergy after a steroid injection and a drink
What it found
A 45-year-old woman had a severe allergic reaction after a steroid injection containing carboxymethylcellulose, and later reacted again to the same ingredient in a hot chocolate drink.
Skin prick tests confirmed the allergy.
What they found
Studies in people
Reaction to injection
The woman developed widespread hives, tongue and throat swelling, low blood pressure and a fast pulse 30 minutes after receiving an elbow injection of Kenalog, which contains carboxymethylcellulose. She was treated in the emergency department and recovered.
Reaction to drink
Three years later, she had hives, chest tightness, light-headedness and swelling of the lips and tongue within 40 minutes of drinking a white hot chocolate powder that contained E466. She was treated in the emergency department and recovered.
Allergy testing
Skin prick testing was positive to Adcortyl, to hot chocolate powders containing E466, and to Celluvisc carmellose 0.5% eye drops, which contain carboxymethylcellulose. Testing was negative to lidocaine and dexamethasone.
Avoidance worked
After her diagnosis, she avoided carboxymethylcellulose/E466 in all food, drink and medications. She had no further allergic reactions for the next 2 years.
Other allergies
She later developed oral allergy syndrome with itching in her mouth when eating raw apple, nectarines, peaches, pears and cherries. Skin prick tests showed sensitivity to tree and weed pollens and to fresh apple.
What the authors conclude
“This case highlights the excipient carboxymethylcellulose as a potential hidden allergen.”
Also in their conclusions
- They say this case highlights the excipient carboxymethylcellulose as a potential hidden allergen, not just in medications but in other consumables.
- They advise that cellulose-containing eye drops provide a readily available and practical way to investigate for allergy in skin prick testing.
- They say it is important to identify excipients such as carboxymethylcellulose as causes of allergy, to reduce the burden of further reactions to drugs and other products.
How it was done
Excipients like carboxymethylcellulose are widely used in foods and drugs and are expected to have low toxicity and low allergy risk. The authors wanted to show that these inactive ingredients can rarely cause serious allergic reactions.
They described one 45-year-old woman who developed anaphylaxis 30 minutes after an elbow injection of Kenalog, which contains carboxymethylcellulose. Three years later she had another allergic reaction within 40 minutes of drinking a white hot chocolate powder that contained E466, another name for carboxymethylcellulose. Skin prick testing was used to confirm the allergy.
What it can’t tell you
- This is a single case report, so it cannot show how often carboxymethylcellulose causes allergic reactions in people.
- It cannot prove that carboxymethylcellulose was the only cause of her reactions, though testing supported it.
Who paid
- Conflicts
- None to declare.
- Authors work at
- St Helier University Hospital NHS Trust, UK
The paper
- Title
- Carboxymethylcellulose excipient allergy: a case report
- Type
- Case report
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Townsend K, Laffan J, Hayman G (2021). Carboxymethylcellulose excipient allergy: a case report. Journal of medical case reports. doi:10.1186/s13256-021-03180-yFree full textPubMed 34819140DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error