With that said, the minor side effects are bruising, a drop or two of blood loss, some minor pains or discomfort, bruising, etc. More severely there's dizziness, blood loss, fainting, headache, etc. Most severely, there is pneumothorax, an increase in complaint issues, punctured organs, drop in blood pressure, etc. The most common side effects I see are actually a sense of relaxation and stress reduction with some minor body aches when physical muscle tension is released.
Keep in mind, that some of the side effects can be mitigated by having the patient eat well before the treatment and be well rested with no drugs or alcohol in the system (except for prescribed meds of course). Also, having the practitioner talk you through the treatment, i.e. checking that you are not uncomfortable, asking if you're ok as they needle, etc. You, as the patient, should definitely speak up if you feel any excess pain or discomfort.
For your tension release, there are two aspects of that. Emotional tension is easily released with minimal side effects, physical pain can also be released easily but may have a side effect of "tired achy muscles" because the muscle itself is releasing it's flex and so becomes tired and sore like after a heavy workout. For that, a liniment or pain patch can relieve the pain and it should clear in two days tops. As far as "wrong points" go, there really is no terrible thing that would happen, it just won't be as effective - it's not like giving a wrong medication with terrible side effects, it just won't be as useful in treatment. In some cases, however, a wrong point can bring an exacerbation of the issue but again, a trained professional should be well aware of proper treatment from diagnosis of pattern.
So, key here is 1. Eat well and rest well before your treatment. 2. No alcohol or drug use for at least one full day before treatment. 3. No excess sexual activity before treatment. 4. Ask questions of your practitioner and make sure they are Licensed Acupuncturists, not just DC's or PT's that had minimal training. 5. Let the practitioner know if you're nervous about anything so they can help relieve your nervousness. 6. Let your practitioner know if anything is making you uncomfortable or causing pain. The practitioner is there to help you and is very concerned about your total wellbeing, so please communicate with them. I promise they will not ignore you like some hospitals do, if they do, go somewhere else for treatment.
Enjoy the experience.
Acupuncture is an excellent way to relieve stress and reduce tension in tight muscles. Many of our patients fall asleep during their treatments only to awake refreshed and relaxed
I have never heard of anyone being severely harmed from acupuncture performed by a licensed, fully trained practitioner (beware: chiropractors, doctors and physical therapists can often do aspects of what we do with significantly less training).
Personally, I prefer Japanese style practitioners and those familiar with the work of Richard Tan for pain and tension treatments. Hope that is helpful!
However, risks of acupuncture include hematoma (bruising at local site), temporary nerve sensations (tingling or sharper pain usually very short-lived), slight discomfort upon needle insertion, fatigue (should a treatment be too strong for the patient), and burns if heat treatment is used. None of the above are extremely common, but can happen. Of the above, the bruising is seen the most.
There are more serious complications, but these stem from physician error, should they be needling against regulations (too deep, too aggressively, and/or over areas of main arteries or areas contraindicated to needling). Thank you for your question.