Laser Hair removal if administered correctly does not have many side effects. The main side effect is pain during treatment which is like a small electric shock-like sensation. However using ice packs or a cold air blower along with treatment often minimises the pain.
The general side effects vary from a slight redness on the treated area to a few black spots as a result of the burnt roots. The swelling usually subsides within a hour. However, if you are undergoing treatment for dark & coarse hair, the roots that have been burnt during the treatment would be visible for a few days. Using a mild scrub on the treated area after a couple of days usually removes these dead roots.
If performed incorrectly LASER hair removal can cause pigmentation problems, especially if high settings are used and the skin is burnt. This is not usually a problem in trained hands. Very rarely some people may experience paradoxical hair growth in areas incorrectly treated. This is usually a problem if light/small hairs are treated by inexperienced practitioners.