Thimerosal allergy and clinical relevance in Thailand.
BACKGROUND
Thimerosal or merthiolate is used as an antiseptic and a preservative in topical medicaments, cosmetics, and vaccines. Thimerosal is known to cause delayed type hypersensitivity. However, there is argument about the clinical relevance and risk of using thimerosal-preserved products in thimerosal allergic individuals.


OBJECTIVE
Retrospective review of patch test results from the Ramathibodi Hospital patch test clinic to determine the prevalence and relevance of allergic reactions to thimerosal in Thailand.


METHODS
During a 5-year period, thimerosal was patch tested in all patients tested for possible allergic contact dermatitis. Thimerosal was the second most common allergen causing a positive patch test reaction.


RESULTS
Of the 433 patients tested, 46 (10.62%) were positive to thimerosal. However, despite the high prevalence of positive reactions none was clinically relevant to their present dermatitis, none of the patients reported reactions to vaccination or cross-reaction to piroxicam.


CONCLUSIONS
There was a high rate of sensitization to thimerosal in Thai patients, but were of little clinical relevance. The author does not advise thimerosal allergic individuals to avoid vaccination, although the small risk of local dermatitis should be pointed out. The topical use of thimerosal containing antiseptics should be avoided.
Wattanakrai
Penpun
P
Division of Dermatology, Department of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok 10400, Thailand.
Rajatanavin
Natta
N
D000293:Adolescent; D000328:Adult; D000891:Anti-Infective Agents, Local / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D017449:Dermatitis, Allergic Contact / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests; D015995:Prevalence; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology; D013849:Thimerosal / Q000009:adverse effects*; D013997:Time Factors
D000891:Anti-Infective Agents, Local; D013849:Thimerosal