Yes, they are real.
In the relics of the saints the Lord Christ has provided us with saving fountains which in many ways pour out benefactions and gush with fragrant ointment (the epithet myroblytus, or “gushing ointment,” is applied to certain saints whose relics exude a fragrant oil). And let no one disbelieve. For, if by the will of God water poured out of the precipitous living rock in the desert, and for the thirsty Sampson from the jawbone of an ass (cf. Ex. 17:6; Judges 15:19), is it unbelievable that fragrant ointment should flow from the relics of martyrs? Certainly not, at least for such as know the power of God and the honor, which the saints have from Him.On the Exact Exposition of the Orthodox Faith by St John of Damascus