What parasitic characteristic causes electrolytic capacitors to be unsuitable for use at RF?

Electrolytic capacitors are constructed by tightly winding long strips of metal foil separated by an electrolyte-soaked dielectric. This physical coiled, spiral construction acts exactly like a coil of wire, inadvertently introducing a significant amount of parasitic inductance into the component. At low frequencies, such as in audio circuits or power supply filtering, this parasitic inductance has a negligible effect. However, as the operating frequency increases into the radio frequency (RF) range, the inductive reactance increases dramatically. This high inductive reactance causes the capacitor to block RF signals rather than pass or bypass them. Therefore, electrolytic capacitors are unsuitable for RF applications, where low-inductance types like ceramic or mica capacitors must be used instead.