The nganga can both heal and harm. Those nganga intended for use to good ends undergo a baptism ceremony and are termed "cristiana" (Christian). Those intended for malevolent ends are left unbaptised and are termed "judía" (Jewish). The latter are used for "trabajos malignos", or harmful work. The boundaries between the two types of nganga are not always wholly fixed, because the baptised nganga can still be used for harmful work on rare occasions. The medical anthropologist Johann Wedel noted that most of the paleros/paleras he encountered during the 1990s claimed that unbaptised ngangas were very uncommon by then.