Electroluminescent Wire for the most part is a very safe product. It is water resistant in its enclosed plastic housing, and uses a low operating current. It converts the voltage into a high frequency (around 2000Hz) which gives a slightly audible sound. Certain casings are able to drown out this frequency better than others, however caution should be used when using EL Wire, Inverters or Battery Packs next to your head. Also exposed EL Wire should never be touched when connected to a power source. This can give you a shock that is unpleasant and unexpected. The most quiet EL Inverter on the market is the Tinko line of EL Inverters. These inverters operate not only at a lower voltage, but a lower frequency as well. This in turn makes for a safer inverter, but also a quiet solution to annoying and loud inverters. 

Warning: Electrical shock can occur when dealing with exposed wires and circuit boards, battery packs heat up after prolonged use and can cause burns when placed on exposed skin for long periods of time, and as with any wire strangulation can occur so keep out of the reach of small children.