Inferno Towers and Healing

I know that Inferno Towers cancel out the healing abilities of healers and the heal spell.

My question is, is the healing canceled out only when the inferno is doing damage to the unit, or from that point on?

In case my question did not make sense, here is an example:

Say I have a healer and a Pekka against an IT. My healer is rendered useless while the IT is doing damage to the Pekka. After the pekka destroys the IT, will the healer's ability begin to work again, or is its ability completely useless from that point on?

Thanks in advance!

I'm relatively certain that the healing is canceled only when the IT is doing damage to the unit. Once the IT is no longer dealing damage to that unit, it can be healed.

The heal is only cancelled when the unit is targeted by the IT. It is not permanently useless.