Although the exact mechanisms that cause EFT to work are still unclear, researchers are beginning to see evidence that tapping on acupressure points works to reverse the brain’s emotional stress response.

In stressful situations, information that comes through our senses gets sent to a region of the brain called the amygdala. The amygdala is part of a set of structures in the brain called the limbic system, which are largely responsible for our emotional life. You can think of the amygdala as being the command centre of our fear-based responses.

When information gets sent to the amygdala, it’s compared with past memories from the hippocampus (also part of the limbic system) in an attempt to assess whether the situation is safe or whether we need to react. When it’s the latter, the amygdala initiates a full-fledged fight-or-flight reaction. This happens faster than our conscious mind can react.

Think of how quickly we launch into a sheer panic when we see our child dart into traffic. You can thank your amygdala for that!

Several studies now show that stimulating certain acupressure points can "deactivate" a hyper-aroused limbic system by communicating directly with the amygdala.

When tapping is paired with negative memories or emotions, as in EFT, the brain is simultaneously exposed to the thing that triggers its fight-or-flight reaction (the memory) and the thing that deactivates it (tapping).

It’s fascinating how this works. By pairing those two opposing signals, researchers think we may disrupt the neurological pathways in the brain that were involved in the fear-based response. (The technical term for this is "depotentiation.")

In colloquial terms, we are literally rewiring the brain when we tap.

--
For a detailed (and technical) look at the possible mechanisms that cause EFT to work, check out:

Feinstein, D. (2010). "Rapid treatment of PTSD: Why psychological exposure with acupoint tapping may be effective." Psychotherapy: Theory, Research, Practice, Training, 47(3), 385.