Although dry needling is an intervention which carries very low risks, there are risk involved. In the context of dry needling the side effects and adverse effects can be defined as follows:
Side effect- Unintended effect occurring during dry needling that relate to the properties of dry needling.
Adverse event- Medical occurrence associated with dry needling, but not necessarily causally related to dry needling.
Here is a fictituous case, were Annie X receives dry needling that may help to highlight the difference.
Annie X has often received dry needling without any issues, but today a small hematoma appears during treatment (side effect). Furthermore, after treatment she reports feeling a little light headed (side effect). Unfortunately, she faints (side effect) in the reception after treatment and hits her head on the edge of the reception counter.
She recovers fully after a few minutes, but has a nasty bump on her head and reports a mild headache (adverse event).
Take care to report adverse events, even if they seem trivial. It is both good ethical practice and a smart legal strategy.