My kids did eat the nut --- maybe I wasn't clear earlier.  After brushing the skin and lips, they ate the partial piece, and then ate a whole nut.  All done in stages.

I'm thinking I want child to actually eat the nut: pieces or whole.

I want child to have the textural experience so that if he/she turns out to be positive, there has been benefit of knowing what to expect so far as the chew/crunch and recognition when embedded in foods.

Not sure how doc wants to handle . . . a few months away, likely.

For the pecan challenge, the nurse first brushed the kids' skin with a pecan and waited --- I don't know, maybe 15-20 minutes.  Then she brushed the kids' lips with it and waited.  After that, it was a piece of a pecan (just asked DS because I don't remember); then they went to a whole pecan.  After the whole pecan and the waiting period with no symptoms, they declared it as a passed challenge.

We got farm-grown local hazelnuts and ground them-- used them in applesauce.

Our dr crunched it up and put various increments in yogurt - they offered to use yogurt, apple sauce or pudding.  Finds it makes it more palatable.  He had increasing doses in spoonfuls of yogurt until he passed. 

Now our allergist was pretty confidant that tree nuts and peanuts were a false positive.  We did one nut first (almonds, I think) and then did three nuts combined three times to finish them off.  Then peanuts were a separate challenge.  Five separate challenges in five weeks.  I missed the peanut challenge because I had the flu.  DH took him and he is not the umm, comforting sort but more of the man up and do it kind of person.  DS1 hated the four nut challenges because they tasted like poo to him (he is still not a fan of tree nuts) and the peanut apparently began with the ultimate fun - DS refused to come out from under the chair.  It's funny now, but I am pretty lucky DH didn't have an aneurysm over it.

GP's dd recently had a pecan challenge. She posted about it.

Almond flour is pretty easy to find, though I don't know how much of it is pure almond.  There always the chance it's X-contam with other substances.

Complete tree nut panel negative and I trust the doc. I'm thinking of starting with almonds first and then hazelnuts because that's what he's most likely to enjoy and eat foods that are cross contaminated with them.

How does your doctor handle the challenge since they're harder substances? Nibble on one? I could grind it up at grandpa's place to powder or paste it.