not that I've tried it, but waterchestnuts add crunch to things, and they don't get soggy... not sure if it's the kind of crunch you're going for, but it's a thought :-)

You wouldn't get the crunch but pecorino romano has a bit of a nutty taste

I was looking around on google and found these alternatives:

pumpkin seeds
chickpeas
edamame

I think any of these would be a great alternative!

what about quinoa?

If it's only pine nuts, pecans and peanuts that are off limits, Blue Diamond almonds are very careful about not getting cross contaminated, and make a delicious pesto.

Otherwise, pumpkin seeds sound delicious...

Oh yes! That's the thing I forgot (I knew there was something...) - Heidi Swanson does a cilantro pesto in her new book and she uses pepitas. It's really amazing - you can see it here.

Breadcrumbs! But first coat them with a little olive oil or butter and toast them. The toasty flavor is a reasonable stand in for nutty, and they'll give you some crunch, too.

I like making pesto with sunflower seeds.

My 2 year old son is allergic to nuts. We use sunflower seeds (the closest flavor to pine nuts), pumpkin seeds and we used to use sesame seeds (until he became anaphylaxis to that too!).I have not used chickpeas UNLESS they are roasted in the oven (then you will get that crunchy texture/Nutty-esq flavor).

Dito on sunflower seed!

(I also often alter the basil and mix in other herbs. :))

Soy "nuts". (If soy is ok!) I usually just buy the crunchy version of Sunbutter (made with sunflower seeds)

I always make pesto with sunflower seeds instead of pine nuts - cheaper and we prefer the taste.

Whalermeg has a good idea, that is, pecorino would make a good substitute for pesto without pine nuts (our recipe doesn't include pine nuts). One note on Pecorino is that you ought to purchase the imported kind from Italy and make sure it's from southern Italy (specifically from Calabria).

Would pumpkin seeds work? the green ones?

I think I'd try pepitos, sesame seeds or soy nuts first. But I just made a barley salad with an heirloom purple barley that was decidedly nutty, so I definitely think it would work. Wheatberries might also be an option.

I put canned garbanzo beans (chickpeas) in my arugula pesto, and while not crunchy, they do add a nice 'nutty' flavor. Here's my recipe:

http://inmykitchengarden.blogspot.com/2006/05/arugula-pesto-takes-over-kitchen.html

I make basil pesto with roasted and salted almonds (as well as some fresh tomatoes), but I'm sure the garbanzos would make a nice substitute. :)

pepitas!

But pine nuts aren't nuts.

They are seeds. http://en.wikipedia.org/wiki/Pine_nut

I use sunflower seeds in mine all the time.
http://somethingstochuon.blogspot.com/2011/08/fresh-pesto-for-lunch.html

I'm in a similar same boat: I can do almonds, but no other nuts; and I can have seeds, but not sesame! I have used almonds, pumpkin seeds, and sunflower seeds with great results (at least to me - having never tried "real" pesto made with pine nuts, I don't have much to compare to!).

As for using chickpeas: unless you roast them first, as was mentioned, you'll just end up with hummus!

Toasted soya nuts or toasted chickpeas will do the trick. I've also used celery, in a very small dice (brunoise, then chill it, mix it in at the last second so it stays crisp), and because the basil overwhelms any celery flavor it adds a nice crunch when I'm preparing pesto for someone who just doesn't like the taste of pine nuts.

pine nuts are not seeds, but one person has an allergy to them all the same. and all nuts- almonds, peanuts, walnuts, pecans, macadamia, etc are off limits.

thanks for all the help everyone- i think sunflower seeds are my best bet.

oops, meant to say pine nuts are not nuts, they are seeds, but the allergy is still the same.

I have a nut allergy and I'm big on clarification, because good info saves lives.

A nut AND seed allergy throws up more issues than a simple nut allergy.

In any case sesame seeds kick ass but might be iffy, and to be fair a banging pesto can be made with out the crunch content. Contamination in processing is something that needs to be taken into account.

For something closer to the pine nut, try hemp seed nut, which is the the meat from the hemp seed. It's really yummy, a little fatty, like pine nuts and would come closests, I think to a substitution. If not that, I'd go with those pumpkin seeds!!

Seeds would be lovely; toasted sunflower (closest in flavour) or pumpkin would give the crunch and suit any coeliacs as well! Best check with your friends first to make sure though... Intrigued about the hemp nut, have to find and try!

Wegmans (awesome Rochester/upstate NY supermarket chain) make a great basil pesto without nuts, the listed ingredients are fresh basil, canola oil, olive oil, water, parmesan and romano cheese blend (plus preservative type things), salt, fresh garlic and lemon juice. I have never noticed the lack of nuts or crunch in it, and my nut-intolerant husband loves it.

We have a nut allergy in the family and tend to use crunchy sunbutter as well. Careful of things that are not technically "nuts" because they are usually handled in the same facilities that process nuts. For pesto, we do a very garlicky, creamy, cheesy version and really don't miss the nuts or substitutes.

If seeds are out entirely, try crushing ramen noodles in a plastic zip top bag with a rolling pin and adding at the last moment before serving. The noodles will stay crisper than fine grain rice, and absorb the pesto flavor.