Some hives are caused by allergies to such things as foods, medications, and insect stings, but the large majority of cases are not allergic, and no specific cause for them is ever found.
Mõned tarud on põhjustatud allergia sellised asjad nagu toit, ravimid, ja putukate nõelamise, kuid valdav enamus juhtudel ei ole allergiline, ja ühtki konkreetset põhjust neid on kunagi leitud.