Freely printed from: https://learn.nimja.com/basics/abreactions
An abreaction is an unexpected release of (suppressed) emotions.
These are often negative and can be subtle, like a bit of sadness, or very powerful like fear, panic and anger.
The reasons behind abreactions are usually unrelated to what is happening on that moment itself. You can compare it with a nightmare.
It looks like any other person in distress and the contrast with their previously relaxed self is usually very obvious.
During hypnosis, you should always pay attention to your subject's well-being and state. If you notice grimaces, twitches, tears, etc. It is important to check with them how they are feeling. It could be fine, it could also not be.
If an abreaction is particularly powerful, you will not be able to miss it.
Remember, not every intense reaction is negative! Please do check with the subject what they are feeling. Give them time to respond and be patient if they don't respond immediately.
Abreactions happen, it's not necessarily anyone's fault. Learn from it what you can, but don't blame yourself more than you should.
In general, it's ill-advised to use more hypnosis to fix something caused by hypnosis. Metaphorically, you've blown out a tire on the highway. Just pull over.
Focus on helping the subject back to their normal state of mind. Do not attempt to fix anything; if you are not a therapist, don't do therapy.
You can use grounding techniques to help them return to where you are:
Since they just went through an intense emotional experience, aftercare is important. A glass of water, gentle caretaking and possibly offering a hug can be very helpful.
Also remember that this may take longer than you think, resetting emotions takes time.
If you are not able to deal with it alone, ask for help. Emotions can be very powerful and dealing with them takes time and experience. Give yourself (as the hypnotist) the time and help you need to deal with this situation as well.