How does ripple degrade electrolytic capacitors?
How does excessive ripple current degrade electrolytic capacitors?


Ripple current causes heat to be generated within the capacitor and electrolyte capacitors degrade faster at higher temperatures.


  Why does ripple current cause heat?


In general a capacitor will heat up due to its ESR alone. With ripple current involved, there is additional heating due to the dielectric losses caused by the changing field strength.


  Why degrade electrolyte capacitors faster at high temperatures?


During the lifetime of the electrolyte capacitor, the electrolyte evaporates. Heat 
accelerates this phenomenon. Runaway failure is possible because degradation can increase ESR and this further increases heat dissipation and temperature.