Curse Backlash (すそ返し, Suso-gaeshi) occurs when an Amasogi is destroyed by anyone but it's user. Curse Backlash takes the form of a sort of punishment on the user and is proportional to the power of the curse that animated the Amasogi.
Due to the sometimes destructive nature of Amasogi, Exorcists must sometimes destroy it or coerce the user to destroy it. If the user destroys the Amasogi then curse backlash will not happen. But if someone else is forced to destroy the Amasogi the curse that dwelled in the Amasogi is released and rebounds off the user. This rebounding effect will have a serious detrimental effect on the life of the user.
Examples of curse backlash that have been seen are hair loss, foul body odor, loss of the ability to walk and speak. Low level curse backlash will fade quickly over time, but very powerful backlash can lead to loss of life or even mass destruction of a localized area.