Do you really need to? Depends on how afraid you are of listeria.
The best part of peeling vegetables is not having to wash them. I love a banana or an orange, because you never need to worry about running them under a tap—they have their own carrying cases. Just peel and go! Why would you make your life weirdly harder by washing a part of the fruit you're not going to eat? This also was my logic with avocados. Why wash them? you're just going to throw away the peel, right? Right?
Well apparently not, according to the Food and Drug Administration, known buzzkills and, I guess, advocates for public health. The FDA issued a report this month advising customers to think about washing their avocados after finding that 17 percent of avocado samples take between 2014 and 2016 had listeria on their skin. Listeria, in case you need reminding, is a very not-fun food-borne illness with symptoms that include vomiting, fever, and diarrhea. It's usually a bigger problem for people with weaker immune systems, but it is still not the way you want to spend your holidays.
How big of a chance is there that listeria on the skin of an avocado will get into the flesh that you're going to eat? It's not a huge percentage. In fact it is 0.2 percent. There is some added concern that the knife you use to cut the skin of the avocado might also drag bacteria into the flesh, but like, there is also some concern that you will be mauled by an escaped rhinoceros while crossing the street. It's possible, but it isn't likely. I wouldn't let it keep you up at night.
If you're someone with a weakened immune system, or serving avocado to children, sure, go ahead and wash it. If you're serving avocado to customers, sure, wash it. If it's just me, at home with an avocado, am I going to wash it? Probably not. I am not a doctor, but I am lazy and might forget entirely. And you know, it'll probably be fine.