Miliaria crystallina is the most common and mildest form of heat rash. If you have miliaria crystallina, you'll notice small clear or white bumps filled with fluid on ...TypesofHeatRashMedicallyreviewedbyAlanaBiggers,M.D.,MPH—WrittenbyKerryLudlam—UpdatedonAugust13,2018PicturesWhatitlookslikeCausesCallyourdoctorPreventionWhatisheatrash?Manydifferenttypesofskinrashesexist.Theycanbeconcerning,uncomfortable,ordownrightpainful.Oneofthemostcommontypesisheatrash,ormiliaria.Heatrashisaskinconditionthatoftenaffectschildrenandadultsinhot,humidweatherconditions.Youcandevelopheatrashwhenyourporesbecomeblockedandsweatcan’tescape.Thecauseofheatrashisoftenfrictiononthesurfaceoftheskin.Adultsusuallydevelopheatrashonthepartsoftheirbodiesthatrubtogether,suchasbetweentheinnerthighsorunderthearms.Babiesoftendevelopheatrashontheirnecks,butitcanalsodevelopinskinfoldssuchasthoseofthearmpits,elbows,andthighs.PicturesWhatdoesheatrashlooklike?Differenttypesofheatrashcanrangeinseverity,andtheyalllookalittledifferent.MiliariacrystallinaMiliariacrystallinaisthemostcommonandmildestformofheatrash.Ifyouhavemiliariacrystallina,you’llnoticesmallclearorwhitebumpsfilledwithfluidonthesurfaceofyourskin.Thesebumpsarebubblesofsweat.Thebumpsoftenburst.Contrarytopopularbelief,thistypeofheatrashdoesn’titchandshouldn’tbepainful.Miliariacrystallinaismorecommoninyoungbabiesthaninadults.MiliariarubraMiliariarubra,orpricklyheat,ismorecommoninadultsthaninchildrenandbabies.Miliariarubraisknowntocausemorediscomfortthanmiliariacrystallinabecauseitoccursdeeperintheouterlayeroftheskin,ortheepidermis.Miliariarubraoccursinhotorhumidconditionsandmaycause:itchyorpricklysensationsredbumpsontheskinalackofsweatintheaffectedareainflammationandsorenessoftheskinbecausethebodycan’treleasesweatthroughtheskin’ssurfaceBumpsthatappearduetomiliariarubracansometimesprogressandfillwithpus.Whenthishappens,doctorsrefertotheconditionasmiliariapustulosa.MiliariaprofundaMiliariaprofundaistheleastcommonformofheatrash.Itcanrecuroftenandbecomec