Why Butternut Squash Hurts Your Hands

October 12th, 2011

Many a gardener will grow butternut squash, and eagerly watch the fruits develop, counting the days, hoping they’re not ruined by an early frost. Then harvest time, and the gardener can’t wait. They take the squash inside and immediately start cutting it up, about 5 minutes later they’re aghast and trying to figure out why their hands are red and peeling and constricted. Water doesn’t help, “What is going on?” they cry.

I was cutting up a butternut squash this morning and my hands got hurt again, just a little bit though, because I was careful to touch exposed flesh as little as possible. It got me wondering about the technical details of why it happened. I knew the broad strokes, as they were, but as a bit of a science geek I wanted to know more. Unfortunately after going on the Internet I found nothing but incorrect information, even Wikipedia had it wrong. You had one forum where some guess made a hearsay guess, and then people cite this as fact, and all over the Internet from forums, to blogs, to Yahoo answers, the incorrect information is repeated.

Suffice it to say, I decided someone needed to put the correct information on the Internet.

Before I tell you why your hands get wounded like they were dipped in acid when handling butternut squash, let me tell you what is NOT the cause.

That is not a residue, or glue, peeling off your skin. Many places attributed this to the sap drying over your skin like some sort of liquid latex, and then peeling off. Your skin is peeling, not a residue, that stuff cracking and falling off is skin. That is why underneath it gets pink, because it is new skin.

This is also not an allergic reaction or contact dermatitis, as so many people seem to think, because one guy found an article abstract that said that some people have an allergic reaction to butternut squash. This condition doesn’t happen to some people, it happens to everyone. It will even happen to different species, in fact a plant treated with the substance will react, and they’re not even in the same Kingdom as mammals.

Which is not to say that some people don’t get contact dermatitis from butternut squash, by all means, if you get a rash, or hives, or end up itchy, you might have that sort of a reaction. Peeling skin is not an allergic reaction.

What is actually happening is you’re getting a taste of the squash’s self defense mechanism. All squashes have this, including relatives like cucumbers and zucchini. In fact, most fruits have this to a greater or lesser degree, even things like apples.

Have you ever noticed how squashes will scab? If they’re wounded they will form a scab. This is one reason they can keep for so long. Have you ever noticed when harvesting a squash, or a zucchini, or a cucumber, the cut end will leak a liquid? That substance is what dries out the end of the stem, sealing it off.

Gardeners perhaps run into this problem more than most because we cook with fresh foods sometimes, right from the garden. Unfortunately in this case right from the garden isn’t best.

Many fruits (and remember, botanically, squash is a fruit) have this self defense mechanism where a sap is excreted when it is wounded to dry out the exposed flesh and seal it off to prevent further infection or damage. There are many animals or insects that have no qualms about eating under developed unripe fruit, the plants, however, want fruits to reach maturity so that it can, in the end, turn into the next generation. So this evolved as a defense mechanism. This astringent compound both results in an unpleasant flavor (unripeness) and it dries out the exposed flesh, creating a scab. So it both deters animals from taking a bite, and heals the bite should they give it a try. You’ll often see that on butternut squash, one bite mark, but no more, the animal learned. Of course animals have evolved too so some will have the gumption to still eat unripe fruits.

As the fruit ripens, this compound lessens. So this compound is less in fully ripe fruit. Some fruits, like butternut squash, are often picked early by gardeners, or the gardener does not realize that the fruit needs to ripen more after picking. This is often referred to as curing. A fully ripened and cured squash will not ooze sap when cut, only newly picked or unripe ones will. The one I cut up this morning was picked slightly under ripe (right before a frost scare that had me worried). I had let it sit for 2 weeks, and I would have let it sit for longer, a month at least, but I really wanted some risotto tonight.

So as you see, this drying agent is just the fruit’s way of self preservation. Without the ability to scab wounds, every scratch, dent, or bite mark would be an invitation to fungus and bacteria, just like on humans, so plants have evolved this ability to scab their wounds just like we have, and this substance that dries out and hardens plants, also dries out and hardens hands, resulting in a painful exfoliation process. To fix it you need to get the substance off your hands, so wash them thoroughly, and then you’ll need some heavy duty moisturizing lotion.

To avoid having this happen to you, make sure your squash are ripe and have had some time to cure and dry out a little bit before you use them, or wear gloves. If you grow your own squash you’ll know when they were harvested, but if you’re buying them this is more common in squash bought in the fall, than in the winter, for obvious reasons. Remember too that this is true for many fruits and vegetables, and you may notice it when peeling a fresh from the garden cucumber and the like, but winter squash are the king of the hill with this, and it is so much worse with them.

I am still interested in learning more about this substance, it is so strong I wonder if it has other uses. Being an astrigent, like calamine lotion, it could probably treat mosquito bites and poison ivy (which is an example of contact dermatitis).

33 Responses to “Why Butternut Squash Hurts Your Hands”

  1. Rob Reel  Says:

    Wow! I had no idea! I’ve never grown butternut squash before and never had to deal with this problem. It’s amazing how nature develops defenses like this, isn’t it? Even plants have learned to defend themselves and ensure the survival of their species.

    Thanks for sharing!

  2. Dunwoody Flowers  Says:

    I love Butternut Squash, but your exactly right with your post. I have planted them in my garden for the last 4 seasons. They usually turn out great except for this last year and they were a little dry because of the weather.

  3. greg  Says:

    wow, I actually just cut one up today and was wondering why my fingers felt like they did. I thought I touched the pan and slightly burned them or something…. wonder how this would work for robbers trying to get rid of their finger prints?

  4. Renee  Says:

    I found this article by surfing for Butternut Squash. This is Good info, and well-written. Thank You! And as Arnold says…I’ll be back.

  5. Teri  Says:

    I agree… seems like since it causes skin to peel it definitely would work for poison ivy (?) or mosquito bites. Fascinating post!

  6. Anna  Says:

    But the fruit of your labor and pain was worth it, right?

  7. Di (The Courtyard Gardener)  Says:

    Well, I never knew that! I am hoping to grow some squash next year, so this is good to know…

  8. Emily  Says:

    Bizarre. I’ve never had that reaction from handling butternut squash. But heretofore it’s all been from the grocery store. Is it that the freshly harvested squash still have the defense mechanisms, but a 2 or 3 day old one does not?

  9. TrishAnna  Says:

    Thanks so much for the info. I had no idea! My skin seems to be a little extra-sensitive to some things anyway, and I learned a while back that I needed to wear gloves (which I hate to do when cooking!) or else expect the results. It’s good to know WHY it happens, and get a handle on other options for avoiding it. Thank you!

  10. J. Thomas  Says:

    Good info to know. I’m planning to start with some vegetable plants for my backyard and I’m looking into what can give the best yield. This additional info is like the bonus gardeners can get if properly harvested. Again, thanks for a great and informative post.

  11. dulcimersong  Says:

    I wonder if this substance would make a good homemade chemical peel for the face……of course it would need to be diluted a bit….but definately an exfoliating agent….hmmm

  12. Kallie  Says:

    Whew…good thing I read this first! Hopefully, I will have my butternut squash soon. However, the ones purchased from the store must not hurt your hands?

  13. Administrator  Says:

    generally store bought ones have cured for long enough to minimize this.

  14. ron tucker  Says:

    The best cure is to wear gloves when handling butternut squash or anything.

  15. catherine Davies  Says:

    Thanks for this very interesting article. I’ve grown butternut squashes for quite a few years and get a good crop. I love the versitility of them in cooking, but have faced the preparation challenges of both cutting them up and the skin peel. I also wondered why it was sometimes worse than other times. More storage required!
    Is this related to Aubergine ‘sap’ too?

  16. Georgia  Says:

    I’m glad that I stumbled over this article! I’m taking a course in plant biology and while studying the wounding responses of different plants it occurred to me that maybe they were responsible for the unpleasantness I have experienced while cutting squash.

    Reading your explanation has encouraged my suspicion (I’m going to confirm this with my professor). The wound-response agents are called Callose (which is present in all plants) and p-protein (present in some plants, including squash).

  17. G.  Says:

    I just chopped up a whole heap of zucchini and squash (bought from the markets) and my hands are a mess! I was freaking out a bit, but now I’ve read this, I feel a lot less worried about my fingers… thanks!

  18. Patricia  Says:

    Well, I just found this post after cutting our last two squash- from our garden- we picked them in November (it’s early March now-they were not quite ripe yet and they sat those 4 months) and I have this strange constriction on my skin. None of the other squash caused this. So apparently it might happen if underripe fruits are picked and then allowed to ripen in a basement for 4 months…hmmm….not thinking we should eat them. Wonder what it does to the lining of the stomach if it can make the skin so uncomfortable and peel.

  19. Administrator  Says:

    The substances is definitely stronger/more prevalent in squash picked under ripe.

    It mainly exists as a defense mechanism while the squash is maturing, once the fruit is mature, ideally it breaks open and decays and fertilizes the next generation, so the plant has no more need to protect ripe fruit.

  20. Nancy Keeler  Says:

    I have always wondered about why the skin on my hands would get tight, discolored then peel off. Thanks to you, I know why. Great blog by the way, Look forward to reading more of it. Your pictures are very descriptive and helpful.

  21. Nicole  Says:

    Is the peel safe to eat? Once it has cured?

  22. Nancy Masek  Says:

    I recall the tightness and the coloration from store bought butternut squash–but skin never peeled, that goodness. (Hot peppers came close!) ..The dates store bought were purchased, sept-march, didn’t seem to matter)n so I am guessing that the store purchased squash were under ripe when initially picked. (even curing will not “solve” the issue, correct?)
    This year, i have grown butternut for the first time. Of course, I will have to guess about first frost…. but as long as the fruit is taken in before that, how long is the cure? If necessary, can they be left in a window inside, and rotated daily? Ya know, one never things about this with tomatoes, or apples, or string beans….should we? and why squash so much, tomatoes are so much more delicate. Thanks… great info.

  23. Nancy Masek  Says:

    “Ya know, one never things”…. should be THINKS.

  24. Lisa  Says:

    Is it still ok to eat? I roasted my squash and really want soup tonight!

  25. sundara  Says:

    amazing!! My husband made some butternut squash last night. My one and half year old boy had some (he was eating it, not touching it) and all night he was itchy, early in the morning i looked at his skin and his skin on legs,arms and face was red ,it looked like he was burned! after few hours it was gone. I just wondered could the same thing that was “burning” your hand be the same thing affecting young organism after eating it?!

  26. Administrator  Says:

    No Sundara, that sounds like a legitimate allergic reaction, either to the squash, or something else your son came into contact with, or it could have been a random coincidental virus. The compound described in my post is eliminated by cooking.

  27. Shirley Koester  Says:

    I have been cooking butternut squash all my married life (52 yrs.) and have never had a reaction to butternut squash until today. We live in Florida, so have to assume that it was imported from somewhere else – perhaps Chili. I had a similar response to the posts above. I make squash soup (which includes butternut and zucchini) often and this is the first time I have had the reaction (staining, itching and peeling).

  28. jeff  Says:

    I peel lots of vegetables as I am a commercial cook. I have always had the symptoms you describe but more recently I have started sneezing when preparing butternuts and then, for half an hour or so, wheezing …. as though I had an asthmatic reaction. Perhaps I should consider a career change. xx

  29. Jamie  Says:

    Thank you for posting this information!

  30. Robin  Says:

    I was relieved to see so many other comments. I had never peeled my squash before cutting them, but decided to do that this time as some of the skins were quite messy. When I finished, my hands were peeling extensively. I panicked and tried washing with many different things from garage hand cleaner to face cleaner with salcylic acid all to no avail. Since my hands were quite tight and still peeling, I finally drowned them in coconut oil (which I knew was good for some people with eczema). The coconut oil seems to have stopped the peeling.

  31. jeremiah  Says:

    Thanks for the info. My wife came to me concerned after cutting up some butternut squash and some spaghetti squash I grew. Her hand was red, dry and cracking. She said it was almost instant after handling the squash. I had a feeling it was something somewhat normal, but this post was great and really set our minds at ease.

  32. Susan  Says:

    Thanks for writing about this. I am an organic farmer and when I harvested the last of the summer squash (some were under-ripe) in the fields in November I got a rash on the web of my right hand (between thumb and first finger) where there had been a whole punctured in my glove. It was slightly itchy with small raised red bumps and spread to the whole back of my hand. It lasted about a month until I sprayed it with a grapefruit seed extract wound spray. It dried and cleared up in two days. Then yesterday I was clearing out the squash that hadn’t kept well due to unseasonal warm temperatures here in California. I developed a similar slight red itchy rash on my hand which spread to the back of my hand. I had been handling the squash on a weekly basis during that time. Yes, I forgot to put gloves on! Used the wound spray this morning and it is clearing up! It seems to be worse where I already had a few open scratches on my hand. Once again, some of the squash I was handling was under-ripe and never fully cured even after being in storage for 2 months.

  33. Susan  Says:

    whoops, that should read winter squash!

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