SACRAMENTO (CBS) – There’s a health alert involving avocados.

The Food and Drug Administration is warning people to thoroughly wash the outside skin of every avocado, even though we just eat the inside.

FDA’s Avocado Safety Report (.pdf)

It turns out one in five avocados tested positive for a bacteria that can cause listeria.

The two-year study from 2014-2016 includes both the domestic and imported kinds of avocados.

Listeria symptoms are flu-like, and include muscle aches, fever and vomiting.