Poisonous secret is a secret that destroys your life even though it’s not your secret. It’s a secret that you’ve been told and told to keep it a secret. But this secret has a profound effect on your own psychological wellbeing. This makes the secret poisonous — you get sick.
You live under the ramifications of something that you never did or experienced. You had no influence of those events/actions and now are stuck under the spell of this secret. The secret is so bad that the person who told you had to get it of their chests and unfortunately chose you.
Since you can’t talk to anyone about the secret but you know that you have to escape the secret. You have one of two options: talk to the person who told you the secret or break their trust and tell someone else.
Of course the third option is to do nothing and let the secret eat you up from the inside.
Of course most secrets aren’t poisonous. In fact secrets only become poisonous in combination with your background. That is to say the person telling you the secret does not realise that, in combination with what you know, the secret takes on another meaning for you.
For example and this is an extreme case. Lets say that someone was involved in a hit-and-run car accident. This person got away. Unfortunately someone else was badly hurt in the accident. The person who caused the accident, if they have a conscience, have a massive pain that they need to resolve. Let us assume they don’t do the right thing, they don’t seek official resolution.
Sometime later the person who caused the accident gets involved in a relationship. Or some other close encounter with a third party. The connection is so close between these two people that the accident causing person has the desire to resolve their secret with this third party.
The third party then becomes privy to the secret. Without having asked to be. The accident-causing person simply needs to relief themselves and the unfortunate third party is the target.
Now it turns out that this third party has a conflict of conscience. Obviously they are intimate with the accident causing person and perhaps neither do they wish to do the right thing. I am not passing judgement here.
However this does not make the secret poisonous per se. Unbeknownst to the secret teller is that the third party happens to be a relative of the person badly injured in the car accident.
And it is this background information of the third party that makes the secret poisonous for them. It is something that the secret teller could or did not know.
This is of course an extreme example. And the fact that the original secret was an illegal act was only used for dramatic purposes. The secret might well be something completely innocuous. The point is that in combination with the background of the receiver of the secret, the secret becomes poisonous for them.
Note that the secret becomes poisonous for the receiver, not the teller. It is important to note that poisonous secrets are in the head of the receiver.