Contact urticaria syndrome due to carboxymethylcellulose in a hydrocolloid dressing

New Challenges in Drug Allergy: the Resurgence of Excipients

Purpose of Review

Allergy to excipients is a cause of multidrug allergy and if it is not taken into account, it can lead to unexpected severe reactions. If an excipient allergy is suspected, an accurate examination followed by algorithms is very important for a correct diagnosis and to give patients detailed information in order to avoid future reactions.

Recent Findings

In recent times, due to allergy COVID vaccine reactions, interest in excipients as polyethylene glycol derivatives (PEGs) has increased as a possible cause of drug and vaccine hypersensivity. In addition to PEGs many other excipients as gelatin, alpha-gal, protamine, benzalkonium chloride, and benzyl alcohol have been described as a cause of allergy to drugs and vaccines. For most excipients, the dilutions used for skin testing (ST) are not standardized and proper algorithms to reach a diagnosis are not available.

Summary

The purpose of this article is to review the excipients that may produce inmediate hypersensitivity drugs and vaccine reactions and update diagnostic procedures to reach an accurate diagnosis. We highlight the in vivo and in vitro diagnostic tests used in published reports and detail the dilution used for each excipient to perform ST in order to confirm this vital pathology and to prevent new reactions.

Pitfalls in drug allergy skin testing: false-positive reactions due to (hidden) additives

Skin testing for drug hypersensitivity is a valuable diagnostic tool and a well established procedure for betalactams and corticosteroids. Although appropriate patch, prick or intracutaneous testing usually permits unequivocal interpretation, the possibility of false-positive reactions must be kept in mind. We report two patients, one with a suspected penicillin allergy and one with a suspected steroid allergy, in whom positive skin tests initially yielded a false diagnosis. In both cases, other findings were inconsistent with the positive skin tests. Therefore, further investigations were performed. After the test preparations had been analysed, the skin test was extended to include the additives, which then yielded the diagnosis of sensitization to the surfactant polysorbate 80 (PS 80, contained in the penicillin test solution) and the emulsion stabilizer carboxymethylcellulose (CMC, contained in the steroid preparation), respectively. It should be noted that positive reactions to test solution additives, as in the first case, may lead to a lifelong false diagnosis of (penicillin) allergy, whereas an undiagnosed allergy to additives in parenteral applications, as in the second case, might prove fatal.

Contact Urticaria from Carboxymethylcellulose in White Chalk

BACKGROUND

Carboxymethylcellulose (CMC) is widely used in consumer goods, foods, and medicaments as a binder, emulsifier, and viscosity enhancer. Cases of immediate and delayed allergic reactions to this anionic cellulose polymer have been reported.

OBJECTIVE

To report a case of contact urticaria from CMC in chalk, with possible cross-reaction to methyl hydroxyethylcellulose (MHEC).

METHOD

Patch tests with readings at 48 and 96 hours were performed with the North American Contact Dermatitis Group standard series and benzisothiazolinone. Open and prick tests with readings after 30 minutes were performed with two brands of chalk as well as with various petrolatum and aqueous dilutions of CMC, MHEC, oleic acid, and calcium carbonate.

RESULTS

The patient developed strong urticarial reactions during open tests with both powdered chalks and had milder reactions to the open test with CMC 10% aqueous (aq) and to prick testing with CMC 0.1% aq. No reaction to MHEC or any of the other ingredients of the chalks was observed. No relevant delayed reaction was noted.

CONCLUSION

CMC can cause contact urticaria. It remains unclear why our patient reacted more strongly to the chalk than to CMC itself. We speculate that the abrasive nature of the chalk enhances the cutaneous penetration of CMC or that calcium carbonate, the main ingredient of the chalk, acts as an adjuvant. It is also possible that CMC and MHEC cross-react and that our negative results with MHEC may be due to improper testing technique or concentrations.