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Walnut skin toxicity

Fixthispleas's picture

My wife and I have both experienced skin burns from black walnut branches and leaves.  We cut a split crotch off of the barn this weekend.  I cut, she chipped.  Where walnut sap contacted her skin, she now has stains and wet blisters.


I had a similar experience a few years ago chipping stump sprouts from the same tree.  I developed extensive chemical burns on my forearms where the branches and leaves rubbed as I shoved them into the chipper!


This seems only to be a problem with wet walnut during the period where the sap is in the upper part of the tree.  We've had no problems with walnut cut and chipped in the fall and winter.


I've also had skin reactions looking like chemical burns from fig and pistachio cut in the summer when the twigs and leaves are full of sap.


And no, the main trunk is only about 12" in diameter so I won't get any good walnut boards from it, just firewood.  Maybe I'll cut a few bowl blanks.

forestgirl's picture

(post #79864, reply #1 of 4)

You really need to protect your skin from future exposures that will produce these reactions.  Otherwise, you're liable to lurch into a more serious allergic reaction that'll end with you in the hospital.  These allergy threads come up 4 or 5 times a year, and some of the outcomes are quite unpleasant and expensive.  Allergic reactions can go from mild to severe without warning if the initial symptoms are ignored.


If you're going to use it as firewood, it'd be best to make sure it's completely seasoned, and even then it might be risky, I dunno.  Whatever you're allergic too, if it gets in your lungs and bronchial tubes, the reaction could be nasty.


forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

Fixthispleas's picture

(post #79864, reply #2 of 4)

Forestgirl, this just doesn't look like allergy to me.  I've spent a lot of  years working in metal finishing and device fabrication and the damage looks like chemical burns to me.  That is, this is not an idiosycratic sensitivity reaction; there's something toxic or caustic in the sap that gives the same kind of burn that sodium hydroxide would leave.


We'll certainly be very careful in the future.  But, we couldn't leave this chuck of tree on the corner of the barn and it was humid (rare here in the great central valley) and 102 in the shade by 1:00.


What amazes me is that we've both been burned by fresh sap.  Yet, dry black walnut is acrid and the dust can irriate the lungs, but many of us work it all the time, love it, and get along just fine with it.  There's clearly lots of chemical change when the wood drys, not just lose of water.


When I slice fresgcut wet black walnut, it's very ugly - a light purple/wet black mess.  Let it dry, and it goes to the superb chocolate brown.


By the way, Forestgirl, if you could spare some "cloudy and 65 degrees", could you send some down this way?

forestgirl's picture

(post #79864, reply #3 of 4)

"if you could spare some "cloudy and 65 degrees", could you send some down this way?"  Would if I could, but we've been seeing 80's-90 and clear skies!!  It does cool off at night, though, so it's quite pleasant.


If those are chemical burns of some kind, I'm stumped.  A substance called "juglone" is the ingredient in walnut that causes problems for other plants, and for horses bedded in walnut shavings (kills the plants, causes laminitis in the horses which is as good as killing them).  However, it's clearly stated in the articles I scanned that humans are not affected by juglone -- in fact, it's been used as an herbal treatment for various ills over the centuries.


forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

Fixthispleas's picture

(post #79864, reply #4 of 4)

I've seen dramatic changes in walnut as it dries.  When I cut wet chunks, the wood is a dirty cream with gray-purple streaking.  It is just plain ugly!  As it dries, it turns a rich dark brown with subtle colored highlights (at least in air dried wood).  I suspect that there are compounds in the sap that are very toxic and/or caustic.  They are naturally present as biocides for fungus and/or insects.  As the wood dries, the chemistry changes.  I think that the Jugalone (the aleopathic herbicidal compound) is the predominant active chemical in dried leaves, twigs, etc, but other compounds can be found in the sap.  Also, the dose makes the poison!  Perhaps a high concentration of jugalone in the sap is dermally toxic where lower dose may or may not be.  This is true of everything from asprin to table salt.


94 today, but humid.  100 tomorrow and sunday, 103 - 107 monday!  Give me October, recall or not!


Edited 7/26/2003 1:15:41 AM ET by telemiketoo