Although the wefts and clip-in hair methods are semi-permanent, they will not cause damage to your hair if installed and removed correctly. You can also ensure that no damage is caused, by using the right remover when taking the extensions out. If you are not a professional yourself we always recommend you to go to a salon or professional hair dresser.
Remember, while wearing the extensions you are not losing the normal amount of hair per day (which is normally from 50-100 strands per day). So when removing the hair extensions after several weeks, all this hair will also come off as well.