The fan could overheat if powered by USB and batteries at the same time, resulting in battery leakage. A leaking battery can cause injury when it comes into contact with the skin.
Smiggle Loopz fan - Line 442678 sold at Smiggle stores and online at smiggle.com from 4 October 2013 to 13 January 2014 ($22.99 each).
What to do
Stop using the fan. Return it to Smiggle for a full refund.