A WORD OR TWO ABOUT GARDENING Caution: these plants might rub you up the wrong way. Althoughplants,includingthosefoundinlocallandscapes,oftencontainanarrayoftoxiccompounds,asurveyofUSpoisoncontrolcentersfoundonly30deathsinthe18yearperiodleadingupto2000.TherewerenoreporteddeathsintheU.S.during2007,thelatestyearforwhichpublishedstatisticsareavailable.Evenso,incidentsinvolvingplantsarethefourthmostcommoncalltopoisoncontrolcentersnumberingmorethan60,000for2007comparedtoalmost55,000forinsecticides.Whileweexpectthepesticidesweuseintheyardtobetoxic(theycarrywarninglabels),plantscomewithnosuchwarninglabels.Thepotentialrisksassociatedwithwhatwechoosetoplantarerarelyconsidered.Wemaybeawareoftheobviousones,spinesandpricklesforinstance,butareoftenunawareoftheunseendangers.Itisimpossibletototallyremoverisk,butwecanatleastbeawareofpotentiallyhazardousplantsinourlandscape,inparticularanythatmightattractachild:thosewithbrightlycoloredfruit/flowersorlargesucculentleaves.Approximately85%ofallplantpoisoningenquiriestopoisoncontrolcentersconcernyoungchildren.Thepresentarticleconcentratesonplanttoxinsthatproducesymptomsasaresultofskincontact(i.e.,contactdermatitis).Asecondarticlewillconsiderplantsthatareinternalpoisonswithsymptomsthatdevelopafterplantpartshavebeeningested.Threetypesofcontactdermatitisarereferredtobelow.Thefirsttwoproducesymptomsrapidly(withinminutes):irritantdermatitisresultsfromdirectphysicaland/orchemicaldamagetotheskin;immunologiccontacturticariaisanimmediatetypehypersensitivityreactionwhichmanifestsasrapidintenseitchingandwelts.Thisreactionisinresponsetothepresenceofforeignproteinsandmediatedbyproductionofaspecificantibody(IgE).Antibodies(immunoglobulins,Ig)areproteinsthathelpneutralizewhatthebodyperceivesasforeign.ImmediatetypehypersensitivityismoreoftenseeninindividualsthatareatopicsensitivetoagreaterrangeofsubstancesbecausetheyoverproduceIgE.Thistypeofallergicresponsetocontactwithplantsisrarecomparedtodelayedcontactdermatitis.Indelayedcontactdermatitis,symptomsdevelop2448hoursafterexposuretovariouslowmolecularweightcompounds(e.g.,componentsinplantsap)towhichanindividualbecomessensitized,andinvolvescytotoxiccells(ratherthanantibodies)oftheimmunesystem.Factorsreleasedbythesecells(stimulatedbythecompoundtowhichyouaresensitized)causethereddening(erythema),intenseitching(pruritis)andnumeroussmalltolargefluidfilledblisters.Thecompoundsintheplantsaptowhichyoubecomesensitizedactashaptens.Afterpenetratingtheskinsurfacehaptensbondwithnormalbodyproteinsmakingthemappearforeignwhichthenelicitstheabovecellularimmuneresponse.Aroids(Araceae)makeupthebulkofplantspeciesmostfrequentlyencounteredbypoisoncontrolcenters.OfparticularconcernareDieffenbachia(dumbcane)andtoalesserdegreeSpathiphyllum(peacelily),Anthurium,Aglaonema(Chineseevegreen),Colocasia(taro),Epipremnum(pothosvine),Zantedeschia(callalilies)andCaladium.

Theirpopularityashouseplantsmakesthemespeciallyaccessibletoveryyoungchildren.Theyallcontainoxalicacid,bothfreeandasmicroscopicneedlelikecrystalsofcalciumoxalate(raphides),locatedinspecialmucilagecontainingcells(idioblasts).Whentheleaf/stemofanaroidiscrushed(orchewed)theidioblasttipsbreakoff.Themucilagethenswellsasitabsorbwateraffectingarapidmassexpulsionofraphides.Oncontactwithsapfrombrokenaroidstems,thereleasedraphidescancauselocalizedirritantdermatitisandeyeinjury.Ifarashdevelopsaftertrimmingtreesorcleaningupafterastorm,checktoseeifyouremovedanyvineshavingsucculentstemsandlargegreencordate(heartshaped)orpinnatifid(highlylobed)leaves.Ifso,thisisprobablythepothosvine(Epipremnumpinnatum).Acultivarwithboldlyvariegatedgreenandyellowleaves,Aureum(someregarditasaseparatespecies,Epipremnumaureum)issometimesseengrowinguptallpalmsorlargetrees.Syngoniumpodophyllum,(arrowhead)vineisanotheraroidthatmaybeencounteredclimbingintoareatrees.BothvinesarecontrolledinMiamiDade(cannotbeplantednearnativeplantcommunities).Potentiallymoreserious,bitingintoanaroidresultsinvastnumbersofraphidespiercingthemucosaofthemouthandthroatliketinyshardsofglass.Apartfromimmediatephysicaldamage(andpain),itissuggestedthatraphidesmaydirectlystimulatethereleaseofhistaminefrommucosalmastcellscausinglocalizededema(swelling)andinflammation.Idioblastsarealsobelievedtoreleasefreeoxalicacidwhichcanresultinextensiveerosionoftheepithelialcellsofthemucosaofmouthandthroat.Otherfactors(e.g.,proteolyticenzymes)havebeenisolatedbuttheirroleintheobservedsymptoms,includinganylossofspeech(asoccurswithDieffenbachia)isnotknown.Duetoanalmostinstantaneoussevereburningsensation,itisrarethatsufficientplantmaterialisingestedforaroidstocauseseriousinternalpoisoning.Althoughswellingofthethroatcouldobstructtheairpassage,thisisinfrequentandinthevastmajorityofcasesexposureprovestobeverypainfulbutfarfromlifethreatening.Apartfromaroids,raphidesoccurwidelyinmanyothermonocotyledons;intheArecacae(palms)raphidesarefoundinstems,roots,leavesandevenflowers.Especiallyhighconcentrationsarefoundinthefruitsofseveralpalmspeciesgrowninlocallandscapesasmanywhohaveremovedfruitingstemsfromaclusteringfishtailpalm(Caryotamitis)canattest.FruitofthedwarfsugarpalmArengatremulacontains1.5xsasmuchoxalateasthefishtailpalm.Bothpalmsarehapaxanthic(stemsslowlydieoncetheybearfruitatwhichtimetheyareusuallyremoved).Oneoptionistoremovetheinflorescencebeforefruitsets,ortofirstcarefullyremovefruit,thencutdownthestem.Otherlandscapepalmswithfruitcontaininghighconcentrationsofoxalateincludebuccaneerpalm(Pseudophoenixsargentii),Macarthurpalm(Ptychospermamacarthurii),royalpalm(Roystonearegia),hurricanepalm(Dictyospermumalbum),spindlepalm(Hyophorbeverschaffeltii)andseveralChamadoreaspp.Ifyoucollectfruitfromthesepalmsforpropagationwearlongrubbergloveswhencleaningfleshfromtheseeds.Anotherfamilyofmonocotyledons,Agavaceae(Agaveamericana,thecenturyplantismostfamiliar)formsixsidedraphidesandcontainsaponins(compoundsconsistingofacomplextriterpenoid,orsteroidcore,towhichoneormoresugarsareattached).

Saponins(alsoreferredtoassteroidalglycosides)arefoundinvariousplantfamilies;somearehighlypoisonouswhentakeninternally,whileotherscancausesevereskinirritation.Thelatterarefoundinagavesandaggravatethemechanicaldamageinflictedbyraphides.Landscapeagavesareonlyrarelyreportedasthecauseofcontactdermatitis.Thefactthatmostpossessfearsomespinesnodoubtwarnspeopletobeontheirguard.Ifyouneedtoremovealargeagave(e.g.,afterfloweringwhentheydie)donprotectiveeyewear,glovesandalongsleevedshirtandusealonghandledcactussaw(definitelynotachainsaw!).Tradescantiaspp.,monocotyledonsintheCommelinaceae(spiderwortfamily),featurewidelyinarealandscapes.Purplequeen,Tradescantiapallida(syn.Setcreaseapallida),inparticular,isawidelyusedgroundcoverwithbrittlesucculentstems.Dependingonsusceptibility,contactwithsapfrombrokenstemscancausemildtomoderateskinirritation,usuallyofatransientnature.Itisnotknownforcertainwhatcomponent(s)inthesapareresponsible,butT.pallidaisknowntocontaincalciumoxalatecrystalsintheformofraphides.TheoysterplantTradescantiaspathaceae,syn.Rhoeospathaceae(acontrolledspeciesinMiamiDade)alsocausesanitching/burningskinirritation.ThereappeartobenoaccountsregardingadverseeffectsfollowingcontactwithathirdspeciesTradescantiazebrina(wanderingsailor)alsousedasagroundcover.Whileraphidesaremostlyfoundinmonocotyledonstheyalsooccur,tovaryingdegrees,in27dicotyledonfamilies.Amongthese,theVitaceae(grapefamily),containonespeciesVirginiacreeper(Parthenocissusquinquefolia)responsibleonoccasionformildtomoderateirritantdermatitis.Asuperficialresemblancetopoisonivyhasleadtothetwoplantsbeingmisidentified.Unlikepoisonivy,whichproducesadelayedcontactdermatitis2448hafterexposure(seebelow),symptomsduetoVirginiacreeperdevelopfarmorerapidly.Theseincludeintenselocalizeditching,inflammationandswelling,theresultofcontactwithsapfrombrokenstemsandbruisedleaves.Suchwasthecaseforalocallandscapecrewclearingvinesfromanovergrownlot.Poisonivywasinitiallysuspected,howeversamplesofthevinebroughttothisofficewerequicklyidentifiedasVirginiacreeper.MembersoftheAnacardiaceaeareresponsibleformorecasesofcontactdermatitisintheU.S.thanallotherplantscombined.OfthesebyfarthemostimportantarefivespeciesofToxicodendroneasternandwesternpoisonoak,poisonsumacandeasternandwesternpoisonivy.Onlyeasternpoisonivy(Toxicodendronradicans)isfoundinsouthFloridaandinMiamiDadeitisinfrequentinresidentialareas.Sapfromalltheseplantscontainsoilyphenoliclipids,urushiols(alkenylcatechols)thatreadilypenetratetheouterlayersofskin.Theyarethensusceptibletooxidiationtomorereactivequinoneswhichactashaptensandbindtoproteinsonthesurfaceofwhitebloodcellsdeeperintheskin.Thesemodifiedproteinsarerecognizedasforeign(antigens)andprimethebodysimmunesystem,sensitizingsusceptibleindividualstofurtherexposure.Whileinitialcontactmayelicitamildskinresponseupto2weekslater,subsequentcontactwithurushiolscausesafarmorepronounceddelayedtypecontactdermatitis(after2448h).

Contactneednotbedirectwithpoisonivybutsurfacescontaminatedwithsap.Thelattercouldbeanythingfromclothing,mulch,gardeningtoolsorevenyourpetsfur(urushiolsareonlyallergenictoprimates).Inadditionurushiolsremainallergenicformanymonths(oryearsincooldryclimates).Intheabsenceoftreatment,fullrecoveryfrompoisonivydermatitistakesabout3weeksdependingonthedegreeofsensitivityandextentofexposure.Approximately1015%oftheUSpopulationistolerant(donotreact)tourushiolexposure,withupto75%inagivenareasensitized(farfewerinlargeurbancenterswherethereislessgreenery).Thedegreeofsensitivityvariesandappearstobegeneticallydetermined,withpeaksensitivitytoexposureoccurringinchildrenbetweentheagesof814years.UrushiolsandrelatedphenoliclipidsarefoundinothermembersoftheAnacardiaceae.Locallythisincludesthenativepoisonwoodtree(Metopiumtoxiferum)whichcontainshighlyallergenicalkenylcatecholssimilartothosefoundinToxicodendronspp.Thisisahazardoustreethatisbestlimitedtoseriousnativeplantcollectors.Twootherrelatedplantsoflocalinterestaremango(Mangiferaindica)andBrazilianpepper(Schinusterebinthifolius)whichcontainlessallergenicalkenylresorcinolsandalkenylphenolsrespectively.Allergensareconcentratedwithinthebark,berriesandnewleavesofBrazilianpepper,whileinmangotheyarefoundinsap,butmoresignificantlyalsointheskinofthefruit(traceamountsinflesh).TheallergensinallofthesemembersoftheAnacardiaceaecrossreactwithoneanothertovaryingdegrees.Forinstance,apersonwhohasbeensensitizedbypriorexposedtopoisonivyisalsolikelytoreacttotheallergensinmangoskin.Thereisevidencethatpersonsraisedinmangogrowingareaswhohaveconsumedmangoregularlyfromanearlyagedevelopatolerancetomangoinducedallergicdermatitis.ThecashewtreeAnacardiumoccidentale)isgrownlocallyinMiamitoalimitedextent.Greatcareneedstobeexercisedinhandlingthenut.Thedoublewalledshellcontainshighconcentrationsofapotentallergenandvesicant,anacardicacid,whichisstructurallyrelatedtothealkenylcatechols(urushiols).Philodendronspparearoidsthatapartfrompossessingirritantraphides,alsocontainalkenylresorcinols.Thesehavebeenassociatedwithadelayedtypecontactdermatitisthatdevelopsinsusceptibleindividualsafterrepeatedcontactwithphilodendronsovermonthsoryears.ThereishowevernoevidenceofcrossreactivitywithextractsobtainedfromToxicodendronspp.PhenoliclipidsarefoundinmembersoftheProteaceaeincludingalkenylresorcinolsinthesilkoak(Grevillearobusta).Appreciatedforitsdelicatefoliageandorangeyyellowflowersitisafastgrowingtreeproducingrapidshade.MorecommonincentralFlorida,itadaptspoorlytolocalalkalinesoilsandishighlypronetostormdamage.Thetreehasbeenreportedasthecauseofcontactdermatitissimilarbutlessseveretothatseeninpoisonivy.PlantsofthespurgefamilyEuphorbiaceaecontainnotonlysomeofthemostdeadlyofallplanttoxins(e.g.,ricin),butdependingonthespeciesthelactiferoussap(latex)cancausesevereirritantdermatitis.Theirritantsinvolved,diterpeneesters(especiallyphorbolesters),arefoundinboththelatexandseedsofmanyeuphorbs.Iftakeninternallytheycancauseseverepoisoning.Skincontactwithlatexresultsinarangeofsymptomsfrommildskinirritationtolocalizedswellingandsevereblistering,

whilecontactwiththeeyescauseintenseburningandpossibletemporaryblurredvision.ThemostcommonEuphorbiafoundinlocallandscapesiscrownofthorns,Euphobiamilii;severalcompactcultivarsandthefloriferousE.xlomihybridshavingstimulatedrenewedinterestoverthepast67years.Thelatexfromcrownofthornsusuallycausesamildtomoderateirritantdermatitiscomparedtothemoreseveresymptomsseeninthelargesocalledcactuseuphorbs.Severalditerpeneestersareknowntoactascocarcinogens(i.e.,theyarenotdirectlycarcinogenic,butmaypromotecancerinconcertwithotherfactors).InthisregardattentionhasbeendrawntothecoincidentaldistributioninE.Africaofpencilcactus,EuphorbiatirucalliwithareasthatexperienceparticularlyhighratesofBurkittslymphoma.Thisisanaggressiveformofcancerfoundmostlyinchildren(extremelyrareintheUS)inwhichtheEpsteinBarrvirusmayplayanessentialrole.Inlocallandscapespencilcactuslatexcancauseintenseinflammation,blisteringofskin(whichcanbeslowtoheal)andsevereeyeinjury.Itisalargeplantwithmanythinbrittlebrancheswhichbreakeasilyreleasingastreamoflatexmakingitespeciallyhazardoustoprune.Althoughpencilcactushasbecomerarerinlocallandscapes,smallplantsaresometimesseeninthesucculentsectionofgardenshops(intendedforwindowsilluse)includingacultivarsoldasSticksonFirewithnumerousthinorangeyredtippedstems.ThisandEuphorbiatrigona(Africanmilktreeorcathedralcactus),anotherpotentiallylargespecies,shouldbeplacedwheretheyareinaccessibletochildren.Thislattereuphorbisalsoavailableinastrikingredformandwhereusedasapottedpatioplanteventuallybecomestoolargeandunwieldyeasilytoppled,especiallyifthespinescatchonclothing.Thecandelabracactus(Euphorbialactea)isanotherlargespecieswithespeciallytoxiclatex,thoughnowmoreusuallyseeninoneofseveraldwarfcristateforms.Highlyornamental,lookinglikepiecesofcoral,theyareusuallygraftedontoEuphorbianeriifoliaandareavailableinareagardenshops.Widelyusedinlocallandscapes,thecrotonCodiaeumvariegatumhasclearsapandwhilenotcausingtheirritanttypedermatitisdescribedfortheaboveeuphorbs,itisassociatedwithdelayedtypecontactdermatitisfollowingrepeatedexposuretosap.Documentedcaseshaveinvolvedfrequenthandlingofcrotons(e.g.,takingcuttings)eitherashobbygardenersornurseryworkers.Theallergeninvolvedhasnotbeenidentified.Incidentally,truecrotons(Crotonspp.)arerarelycultivated,butcontainatleastoneespeciallypoisonousspeciesCrotontiglium,theseedsofwhichwereonceusedasapurgative.Isolatedinstancesofallergicdermatitishavebeenrecordedaftercontactwithanothereuphorbfoundinlocallandscapes,thechenilleplant,Acalyphahispida.ThemanchineelHippomanemancinella,nativetosouthFlorida(andsouthtoColumbia)findslittleuseasashadetreedespiteitsattractivefoliagebecauseofhighlyirritantsap.Useofthetreeforshadehasprovedunwise,finedropletsofsapdrippingfromthetreehavebeenknowntocausepainfulskinblistersandtemporaryeyeinjury.TheApocynaceaeisanotherfamilycharacterizedbymilkylatex.Whilecertainspeciesareextremelypoisonousiftakeninternally,contactwiththelatexisaninfrequentcauseofirritantdermatitis.Thelatexfromallamandas,Plumeriaspp.(frangipanis)andAdeniumspp.(desertrose)maycausemildirritation.Unidentified

allergensincrushedoleander(Neriumoleander)leaveshavebeendocumentedasthecauseofdelayedcontactdermatitis.LatexisalsofoundinmanymembersoftheMoraceae.Ediblefig(Ficuscarica)latexcontainsaproteolyticenzyme(ficin,usedtotenderizermeat)thatinpartisresponsibleforanirritantdermatitis.SeveralsmallproteinspresentinthelatexofFicusbenjaminahavebeenassociatedwithimmunologiccontacturticariaaswellashayfeverlikesymptoms(immediatetypehypersensitivity)insusceptibleindividuals.Somecrossreactivitywithnaturalrubberlatexisalsoseen.TheleavesofF.caricacontainfuranocoumarins,contactwithwhichisassociatedwithphytophotodermatitis.Followingcontactandexposureofskintosunlight,severeerythemaandblisteringdevelopoverthenext48hoursoftenfollowedbyaperiodofprolongedhyperpigmentationofaffectedskin.MembersoftheRutaceaealsopossessphotosensitizingfuranocoumarins.Bergapten(foundinoilofbergamotfromCitrusbergamia)isinlargepartresponsibleforthephotodermatitisthatmayfollowcontactwithlimes(moresoPersianthanKeylimes).Hayfever(immediatetypehypersensitivityreactiontopollenantigens,IgEmediated)isanalltoofamiliaroutcomeofexposuretomanymembersoftheAsteraceae(Compositae).Delayedcontactdermatitisisfarlesscommonandmostoftendevelopsinmiddleagemen.Ratherthanreactingtotheproteinantigensofpollenitinvolvesrepeatedexposuretolowmolecularweightcomponents,notablysesquiterpenelactones,foundinleavesandstems.Manyofthesecompoundsarerelativelybenign(tastebittertowardoffherbivores),andsomehaveimportantmedicinalproperties,e.g.,artemisininfromChinesewormwoodasanantimalarial.Onlysesquiterpenelactoneswithaparticularchemicalconfigurationareallergenic,(i.e.,functionashaptens,bondwithproteinssoastomakethemappearforeign).WithintheAsteraceae,thelandscape/houseplantsmostoftenfoundresponsiblefordermatitisarechrysanthemums(crossesinvolvingDendranthemagrandiflorum).ThereareotherornamentalspeciestowhichsusceptibleindividualscanbecomesensitizedincludingTagetesspp.(marigolds),Helianthusspp.(sunflowers),Tithoniadiversifolia(Mexicansunflower),Pseudogynoxyschenopodioides(syn.SenecioconfususMexicanflamevine)andGamelopsischrysanthemoides(Africandaisybush).TheAsteraceaecontainsfamiliarhighlyallergenicweedssuchasragweed(Ambrosiaartemisiifolia)that,inadditiontobeingimportantcausesofhayfever,arelinkedtodelayedcontactdermatitis.Partheniumhysterophorus(partheniumweed)isacommonweedlocallyintheRedlandfarmingdistrict.InIndiaandAustraliaithasbecomeaserioushealthproblemandisresponsibleforwidespreadairbornedermatitisduetocontactwithdriedwindblownplantparts.PlantsintheAraliaceaecontainvariouspolyacetylenes,especiallyfalcarinol,whichcancauseirritantdermatitisandlessoftensensitizesusceptibleindividualstoadelayedcontactdermatitis.Mostreportsconcerncommonivy;howeverofmorepotentiallocalrelevanceScheffleraarboricola(dwarfschefflera)alsocontainsfalcarinolandhasbeenlinkedtodelayedcontactdermatitis.Variouscultivarsofthisshrub,especiallyTrinettearewidelyusedinarealandscapesandgrowncommercially(usuallycuttings).Symptomsaremostlikelytodevelopfollowingahistoryoffrequent

contactwithcutstemsorbruisedleaves(duringpruningortakingcuttings)whenexposuretosapismorelikely.IrritantdermatitishasalsobeenreportedaftercontactwithPolysciasspp.(aralias)allpartsofwhichcontainsaponins,pluspolyacetylenesinatleastonespecies,Polysciasfruticosa(mingaralia).Theaboveplantfamiliesarethosemostcommonlyfoundinlocallandscapesthathavethepotentialtocauseirritantand/orallergicdermatitis.Sensitivitytoagivenplantvariesandinmanycasessymptomsmaybemildoronlydevelopafterrepeatedexposure.Ifyousufferanirritantdermatitiswhenworkingintheyardandcannotlinksymptomstocontactwithoneoftheabovegroupsofplants,thelistisnotexhaustive.Inadditiontherearenonplantcausesofirritantdermatitis.Plantsmayhavebeensprayedwithachemicalorharborunseeninsectse.g.,contactwiththenativelittlefireant,Wasmanniaauropunctataoroneofseveralcaterpillarswithurticating(stinging)hairs/spines).IfyouhaveanyconcernsaboutsymptomsthatdevelopafterindoororoutdoorcontactwithplantscallPoisonControl18002221222Yes,itshotandhumidformostoftheyearinMiami.Nevertheless,whendoingyardworkwearalongsleevedshirt,longpantsandgloves.Thiswillprovideprotectionfromskincontactwithplantmaterialespeciallythatscatteredbypowerequipmentsuchaslinetrimmers(wheneyeprotectionisalsoadvisable).Beextracarefulclearingoutovergrownareaswhereyouarentquitecertainwhatmighthavesproutedup.Thisisparticularlyimportantifyouaretakingoverapreviouslyrepossessedpropertywithayardwhichmayhavebeenneglectedforanextendedperiod.Ifyouarentcertainastotheidentityofplantsinyouryardtakecuttings(notjustaleaf!)toyourlocalExtensionoffice.IamindebtedtoJeffreyBernsteinMD,MedicalDirectorFloridaPoisonInformationCenterMiamiOffice,forthebenefitofhisexpertise.JohnMcLaughlin October5,2009

A WORD OR TWO ABOUT GARDENING Caution: these plants might rub you up the wrong way.