I use a lot of analogies in explaining medical issues to my patients.  Case in point is the double edged sword which cuts both ways.  In other words, it can be used for both good & bad.  A good example of this double edged sword is the non-steroidal anti-inflammatory drug (NSAID) class of pain relievers.  They do a great job of relieving pain & reducing both inflammation & fever.  However, they do so no without risk such as gastritis, peptic ulcer disease, and even gastrointestinal hemorrhage.  They can also injure the kidneys and increase blood pressure so clearly, their use needs to be monitored closely.