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Is Walnut dangerous/toxic

shadyjim's picture

I've heard shavings and dust from walnut can be dangerous to animals and to humans.  Our local vet said he'd heard it was a problem for horses but he didn't know about humans or dogs (I've got Labradors).  Anybody know anything about this?

drwatson's picture

(post #77422, reply #1 of 17)


This has been discussed before.  A check of the archives should give you a lot of information.

nikkiwood's picture

(post #77422, reply #2 of 17)

All my planer shavings go to a horse owner for bedding. She will take anything except walnut, since it is terrifically toxic for horses. She told me exactly why, but it seeped through my sieve-like brain.

I seem to also remember (from the thread cited above) you should not mix it in with your compost pile.

I have never heard that it is abnormally toxic for humans. Dogs? -- can't say.

*** "It is what we learn after we think we know it all, that counts." John Wooden ,1910-2010

Fixthispleas's picture

(post #77422, reply #3 of 17)

Walnut has some real toxic issues:

- It's aleopathic. In normal folk english, it has natural herbicides (jugalone) that surpress the growth of other plants. Compost walnut dust and shavings before using as mulch.

- It's a respiratory irritant. I speak from experience as an adult onset asthma patient. If I sand walnut without dust collection and a dust mask, I develop asthma symptoms within a few hours.

- It can be a skin toxin. Some years ago, my wife and I cut a bunch of walnut stump sprouts from some stumps near the barn and chipped them in early summer when the sap was running. Several days later, my arms had third degree chemical burns from the chain saw dust and sap that took two months to heal!

All of the dark woods are dark because they have natural biochemical WMDs that fend off rot, insect attack, and plant competitors. Use respiratory protection, collect the dust, and be especially careful if you're sweating and dust can accumulate in your wet spots.

Nature can produce toxins every bit as deadly as man can. Botulism toxin beats even sarin hands down. Don't be a limbuagh and poo poo warnings; use respiratory protection and avoid contact with sweaty skin.

By the way, all that walnut I cut and air dry on this little property is gorgeous beyond anything you'll find at your hardwood supplier!

nikkiwood's picture

(post #77422, reply #4 of 17)

Yours seems to be a particularly adverse reaction to walnut. Do you have similar problems with any other wood species?

*** "It is what we learn after we think we know it all, that counts." John Wooden ,1910-2010

jackplane's picture

(post #77422, reply #5 of 17)

I've never had a bad reaction to walnut. But I know OSHA has pointed out that walnut sawdust can cause nasal cancer, so a respirator makes good sense.

Expert since 10 am.

Norse's picture

(post #77422, reply #12 of 17)

Compost walnut dust and shavings before using as mulch.

I recently talked to a plant toxicologist at Cornell who said that jugalone in not water soluble, therefore, will not degenerate as it composts. 

I put my walnut shavings around plants (weeds) I'm trying to control but the thistle seems to thrive on it!


shadyjim's picture

(post #77422, reply #13 of 17)

Thanks to all you folks.  Appreciate the info.

mezzomom's picture

(post #77422, reply #14 of 17)

Hi! I'm a visitor to this forum and this thread caught my attention. I was looking for info about inlay techniques for a gamebox I'm building out of some black walnut lumber we've had for several years. (We have 1100 LF of 1x7 T&G walnut that was left over from the paneling of a logging baron's 1930s mansion. There's a long story to how we acquired it.) We were going to use it for flooring when we built our cabin three years ago, but opted for cork instead. (I highly recommend cork, BTW!) I've finally gotten around to using it for a big project requiring a lot of cutting, sanding and glueing up. The work is going slowly, however, because for every evening I've spent working, I've had to take several days off to recover from the ache in my sinuses and head. I thought maybe I wasn't getting the wood cleaned well enough before working and that some kind of extra fine dust from my Dad's barn was getting through my simple dust mask. Apparently I'm going to have to get a respirator. Thanks so much for helping to clear up this mystery for me!


HowardAcheson's picture

(post #77422, reply #15 of 17)

If you are getting a reaction from inhaling the walnut dust, you may also be getting a reaction from dust getting into your eyes--it runs down the tearducts into your nose. Some also develop a reaction from just getting the dust on the skin.


mezzomom's picture

(post #77422, reply #16 of 17)

Thanks, Howie.  I guess I should trade in my safety glasses for some goggles.



jonsherryl's picture

(post #77422, reply #6 of 17)

shad, you've gotten good feedback on this thread so far...and a trip to the archieves should produce even more background information...But here are the key points:

Walnut contains two extractives that are pharmacologically very potent; juglone and ellagic acid.

JUGLONE is a natural herbicide, which the tree releases through its roots, to fend off competing vegitation. It is also found in the wood itself and is probably one of the extractives involed in the development of walnut's dark pigmentation. As for how it affects humans and other animals, it is both an irritant and an allergen. A small, but meaningful percentage of woodworkers find it irritating in that, given heavy exposure to the dust, it causes skin rash and/or respiratory problems. For those very few woodworkers who develop an allergy to it, even trace amounts can cause a serious reaction.

ELLAGIC ACID is a rather potent sedative, even for humans, but it seems that some livestock and pets appear to be especially sensitive to it. In fact, the Forest Products Laboratory reports one case where a dog chewed on a walnut carving and fell into a deep sleep lasting 48 hours (the study didn't report what the owner did to the dog when it woke up :O) ).

Walnut also contains some tannins which are capable of causing irritation to people who have particularly sensitive skin, but the oaks are far more potent in this regard.

...So, the bottom line appears to be that caution is warranted when dealing with least for the first few times you use it (allergies typically require some prior exposure before they really kick in). If it appears your problem is simple irritation, it can be minimized by a good dust collection system and/or wearing a respirator...On the other hand, if you discover that exposure to even minute amounts of the dust cause a serious allergic reaction, then you should leave this wood alone...and probably also any other species in the walnut genus: Juglans...since all of them contain juglone in various amounts.

Fixthispleas's picture

(post #77422, reply #7 of 17)

Jon, the asthma response can be ascribed to the properties you cite, but the skin burn is a different animal. Most of the work done on wood toxicity is done with the wood sometime after cutting.

The really serious burn I got was late spring when the sap was flowing at its max. I've both worked walnut and even cut and chipped more walnut than I'd've ever dreamed, but I've only had a reaction when the sap is up and flowing.

The morale: I recommend cutting and chipping walnut when somewhat dormant if possible - especially fresh shoots and verdant green leaves!

jonsherryl's picture

(post #77422, reply #8 of 17)

I'd go along with that, Mike. Juglone, in it's stable form, might have different allergenic properties from the precursors (hydrojuglone) that combine to form it. They are more water soluble...and if you were allergic to just one of these precursors, your skin might absorb it more easily.

I haven't seen any research on this aspect of juglone...but I think what you are saying is certainly plausible.

Fixthispleas's picture

(post #77422, reply #9 of 17)

We've found that the pistachios act similarly. We rarely trim or prune in the active growing season, but, when we do, the sap is acrid and caustic and can blister our skin. In the late summer when we harvest, the sap is drier and begining to get rubbery. In fact, it coats our hands while we're harvesting, but isn't the slightest bit irritating.

I would think that exprienced hardwood loggers would have tales about when to harvest and when not to.

jonsherryl's picture

(post #77422, reply #10 of 17)

Mike, pistachio is in the poison ivy family (Anacardiaceae) and it's a wood that also bothers a lot of people...but the chemistry of the allergens in it is substantially different from that of walnut. The offending extractives in pistachio are chemically more like those found in silky-oak (AKA; lacewood), even though silky-oak belongs to a completely different family (Proteaceae) ...I believe these allergens are quinones ( a group of hydrocarbons) found in many hardwoods...and the quinones tend to be at the source of many allergies...Unfortunately, I'm not enough of an organic chemist to explain the whys and wherefores.

HowardAcheson's picture

(post #77422, reply #11 of 17)



Founder from Black Walnut Shavings

Founder (laminitis) can be induced by black walnut shavings. Researchers have long suspected the poison from black walnut leaches up through the horse’s hooves and the sensitive laminae into the bloodstream and becomes systemic. Stalled horses may ingest some of it from the floor from nibbling their hay.

As little as 5% black walnut shavings mixed with 95% pine shavings in a 12 x 12 stall can be fatal to a horse within 12 hours.

Clinical signs (as soon as 8 hours after exposure) are increased heart rate, increased respiratory rate, depression, high body temperature, acute laminitis (rotation of the coffin bone) and sometimes colic.



Vslynch92's picture

My boyfriend got something on (post #77422, reply #17 of 17)

My boyfriend got something on his face from cutting down a walnut tree and we can't get it off. It's like SAP or something. Any ideas?