Acta Dermato-Venereologica 97-6 97-6CompleteContent | Page 31

SHORT COMMUNICATION 767

Advances in dermatology and venereology Acta Dermato-Venereologica

Insect Repellents and Contact Sensitization: An Observational Study

Monica CORAZZA 1, Annarosa VIRGILI 1, Alberto Maria BERTOLDI 1, Giulia TONI 1, Dario CRISTOFARO 2 and Alessandro BORGHI 1 *

1

Department of Medical Sciences, Section of Dermatology and Infectious Diseases, and 2 Department of Chemical and Pharmaceutical Sciences, University of Ferrara, via L. Ariosto 35, IT-44121 Ferrara, Italy. * E-mail: alessandro. borghi @ unife. it Accepted Mar 16, 2017; Epub ahead of print Mar 17, 2017

Use of insect repellents is an inexpensive and practical measure for preventing insect bites, through producing a coating that has a smell or flavour that is offensive to insects( 1 – 3). Many compounds, both natural and synthetic, have been used for their repellent activity against arthropods( 4 – 6).

The number of cases of allergic contact dermatitis due to insect repellents reported in the literature is small despite their widespread use and the increasing number of available products( 3, 7).

The aim of the present study was to investigate the prevalence of sensitization to insect repellents in the territory of Ferrara, located on reclaimed lagoon areas in the north of Italy, an area characterized by an exceptional presence of mosquitoes.

MATERIALS AND METHODS

A total of 106 consecutive patients, 72 females( 67.9 %) and 34 males( 32.1 %), presenting to our dermatological department for various skin complaints, were enrolled for allergological investigation. All the patients gave their written consent. The following data were collected: demographics, occupation and hobbies, specifying whether indoor or outdoor, previous dermatoses, history of atopy, and use of insect repellents, specifying the kind of repellents used.

All patients were patch-tested with the Società Italiana Dermatologia Allergologica Professionale Ambientale( SIDAPA) baseline series( Lofarma S. p. A., Milano, Italy) as well as an additional insect repellent series, containing 10 insect repellents selected among those commercially available according to frequency of use in commonly marketed products: dimethyl phthalate 5 % pet, eucalyptus oil 2 % pet, lemon oil 2 % pet, citronellol 2 % pet, pyrethrum 2 % pet, dibutyl phthalate 5 % pet, diethyl toluamide( DEET) 1 % pet, menthol 1 % pet, thymol 1 % pet, hydroxycitronellal 5 % pet. Insect repellent allergens were supplied by F. I. R. M. A. SpA, Florence, Italy. Allergens were applied on Finn Chambers on Scanpor ®, SmartPractice, USA. Patch test readings were performed at 48 and 72 h. To avoid misinterpretation, doubtful results were not considered.

The results of the patch tests were recorded in a database and statistically analysed. Binary data were analysed with χ 2 or Fisher’ s exact test according to conditions. Quantitative data were analysed by means of Student’ s t-test, in the case of normality and homoscedasticity, or, alternatively, by means of Mann-Whitney U test. Statistical significance was defined as p < 0.05.

RESULTS

Eighty-seven patients( 82.1 %) reported using insect repellents on a regular basis, mainly aerosol and pump sprays. Forty-four patients( 41.5 %) proved positive to at least one allergen of the SIDAPA baseline series. Concerning the insect repellent series, 8 patients( 7.5 %) showed 12 positive reactions( Table I). Among these 8 sensitized patients, all but one referred a regular use of insect repellents. The risk of having at least one sensitization among the regular users was no different from that of the other subjects( odds ratio( OR) 1.5287, 95 % confidence interval( 95 % CI) 0.1775 – 13.1675, p = 0.574, Fisher’ s exact test). The occurrence of positive reactions was not related to the type of topical repellent used( p = 0.629, χ 2 test). Regarding the frequency of sensitization, there were no significant differences by sex( p = 0.437), indoor / outdoor occupation( p = 0.560), indoor / outdoor hobby( p = 0.445) and atopic diathesis( p = 0.546) according to Fisher’ s exact test. On the other hand, the patients sensitized to repellents were found to be younger than the others( p = 0.010, Student’ s t-test).

Among the 8 patients with positive reactions to repellents, 7 had at least one positive reaction to common allergens of the SIDAPA baseline series, for a total of 14 concomitant reactions. The risk of being sensitized to common allergens was higher among the subjects sensitized to repellents compared with patients without any sensitization to them( OR 11.5405, 95 % CI

Table I. Positive reactions to allergens of the insect repellents series and concomitant sensitizations to allergens of the baseline series Pat. No. a Insect repellents series Società Italiana Dermatologia Allergologica Professionale Ambientale( SIDAPA) baseline series

a The reported numbers correspond to the consecutive ones attributed to the patients at enrolment; MCI / MI: methylchloroisothiazolinone / methylisothiazolinone.

This is an open access article under the CC BY-NC license. www. medicaljournals. se / acta Journal Compilation © 2017 Acta Dermato-Venereologica. doi: 10.2340 / 00015555-2653 Acta Derm Venereol 2017; 97: 767 – 768