Correlation ofInVitroChallenge Testing withConsumerUse Testing forCosmetic Products

Aninvitro microbial challenge testhasbeendeveloped topredict thelikelihood ofconsumer contamination ofcosmetic products. Thechallenge testinvolved inoculating product atfourconcentrations (30,50,70,and 100%)withmicroorganisms knowntocontaminate cosmetics. Elimination ofthesemicroorganisms ateach concentration was followed over a 28-day period. Thetestwas usedtoclassify products as poorlypreserved, marginally preserved, or wellpreserved. Consumeruse testing was thenusedtodetermine whetherthetest predicted theriskofactual consumer contamination. Productsclassified bythechallenge testas poorly preserved returned 46to90% contaminated after use. Productsclassified by thechallenge testas well preserved returned withno contamination. Marginally preserved products returned with0to21% oftheused units contaminated. Asa result, thechallenge testdescribed can beaccurately usedtopredict theriskof consumer contamination ofcosmetic products. Theworkdescribed addresses thecriticism thatmicrobial challenge tests usedinthecosmetics industry areunreliable aspredictors ofaproduct's ability toresist microbial contamination fromconsumer use.Thecriticism isbasedonthe contention thatchallenge testdataarenotvalidated by consumerusedata(17). TheFoodandDrugAdministration expressed its concern aboutin-use preservative adequacy of cosmetics inaFederal Register notice in1977. Thisnotice stated thatregulatory action wouldbetaken"toremove fromthemarketanycosmetic thatposesanunreasonable riskofinjury because ofinadequate preservation towithstandcontamination undercustomary conditions ofuse" (18). Industry hasbeenresponsive tothis concern. Asearly as1970, cosmetic trade associations andindividual companiesrecommended thatconsideration begiven tocontinued effectiveness ofa cosmetic's preservative systemunder intended consumeruseconditions (11,20,31).Morerecently, consumertestprograms toassess in-use preservative adequacy havebeendescribed (21).