Dermatitis®

Counseling of patients with cocamidopropyl betaine (CAPB) allergy is difficult because the cross-reactivity of CAPB with other coconut-derived surfactants, coconut oil, and coconut fatty acids is largely unknown.

To provide pilot data regarding the cross-reactivity and allergenicity of surfactants derived from coconut oil.

A randomized double-blind controlled pilot study of 10 control patients and 12 patients previously found to be allergic to CAPB. Eleven coconut-derived surfactants, as well as coconut oil and lauric acid, were applied in random order according to standardized patch-test procedures with readings at 48 and 92 hours. The primary outcome measure was the frequency of positive patch-test reactions to each allergen.

Only 3 of the 12 patients with previous reactions to CAPB reacted on retesting, and all of these reactions were doubtful. Fifty-nine percent of the study patients had reactions to triethanolamine polyethylene glycol-3 (TEA-PEG-3) cocamide sulfate as compared to none of the controls (p = .005).

Reactions to CAPB were only 25% reproducible. These results substantiate previous experience that doubtful and mild reactions to CAPB may represent irritant reactions as opposed to true allergic reactions. TEA-PEG-3 cocamide sulfate was the only agent that had a statistically significant higher rate of reactions in the study group as compared to the control group.

Studies suggest that the Thin-Layer Rapid-Use Epicutaneous Test (TRUE Test) may be inadequate to completely diagnose a significant number of patients with allergic contact dermatitis (ACD).

To study the usefulness of the TRUE Test as a triage tool in a private practice setting.

A retrospective chart review of patients who were patch-tested with the TRUE Test between July 1, 2000, and June 30, 2004, in four private dermatology practices was conducted.

Of the 183 patients evaluated, 50.8% had at least one positive reaction, 31.7% had a diagnosis of ACD, and 24.0% were suspected to have ACD from other allergens. Of the patients with positive reactions, 62.4% were determined to have reactions that were of present relevance.

The TRUE Test allows patients with dermatitis to be triaged systematically in a private practice setting. It is important to supplement patch testing with the patients' personal products, especially in cases of facial or periorbital dermatitis, and to be aware of potential false negatives, particularly with fragrance and rubber additives.