Contribution of cysteine and serine proteases to proteolytic digestion in an allergy-eliciting house dust mite

•Body-associated proteolytic activity in HDM is dependent on cysteine proteases.•Major allergen Der p 1 accounts for most of the cysteine protease activity.•Fecal-associated proteolytic activity depends on cysteine and serine proteases.•Ingested cystatin A, by inhibiting Der p 1, impairs activation of serine proteases.•Feeding experiments demonstrate the autocoprophagic behavior of the mite.