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The Surprising Link Between Mango and Poison Ivy

How a compound called urushiol can lead to ‘mango mouth’

Could this delicious looking mango… lead to DEATH?!? (Probably not, but it could give you a minor reaction!)

When I moved from studying as a graduate student into the corporate world of Silicon Valley, perhaps the most surprising discovery was the variety of free snacks available.

Our workplace, like many others that I visited, offered a “snack wall” with myriad options for peckish employees. We had granola bars, cereal, yogurt, and chips, of course, but I found myself gravitating towards dried fruit — and one dried fruit in particular.

Mango is that perfect combination of sour and sweet — which has earned it many fans worldwide. It’s the national fruit of India, Pakistan, and the Philippines, and humanity has been consuming them for more than 5,000 years. That means that we’ve been growing and eating mangos since before the Egyptians built the Sphinx and the Great Pyramids. We were snacking on mangos long before we built the Great Wall of China.

But for some individuals, mango isn’t a delicious treat. Instead, it’s a food to avoid, along with cashews and pistachios. Sufferers experience contact dermatitis, due to the presence of a compound called urushiol.

Many of us, especially camping enthusiasts, have likely encountered urushiol before. It’s an oily mixture of organic compounds, and it’s most often encountered in poison ivy, poison oak, and poison sumac.

Yeah, those itchy rashes that you may get if you encounter poison ivy? For some people, mango (or cashews, or pistachios) can trigger the same reaction.

Why do some people react to the urushiol in mango, while others do not?

And how does urushiol work on us, and what can we do to minimize the irritation, pain, and suffering?

How We (Physiologically) React to Poison Ivy

When we’re exposed to poison ivy, or other poisonous plants in this family (including poison oak and poison sumac), we’re actually being exposed to urushiol that’s present in the sap of these plants.

When the plant is damaged, the urushiol-containing sap leaks to the surface. The purpose of this sap, interestingly enough, is not to serve as a defensive mechanism; instead, it forms a black lacquer when exposed to oxygen, helping the plant retain water.

Our reaction to urushiol exposure varies from individual to individual. About 20% of individuals don’t have a reaction from exposure, 60% of individuals will have a moderate reaction, and 20% of individuals will have a very strong response that results in serious, prolonged symptoms.

Interestingly, the response grows stronger with repeated exposure. This means that, while someone may not get an allergic reaction when first exposed, subsequent future exposure may trigger a reaction.

Urushiol is absorbed quickly into the skin, with about 50% of the compound absorbed within the first 10 minutes. This is why, if exposed to poison ivy, poison oak, or poison sumac, it’s important to wash with soap and water right away, to remove the oil that has not yet absorbed!

Once it’s on the skin, the molecule oxidizes, and then bonds with membrane proteins of our cells. Our immune system no longer recognizes these cells with bonded urushiol, and attacks them, leading to an allergic reaction.

Treatments for urushiol exposure fall into one of two stages — immediate or delayed.

• Immediate treatments, after recent exposure, involve washing the affected areas with soap, to remove the oil, and a scrubbing agent, to help separate the oil that has bonded with the skin.

• Delayed treatments, once the oil has been absorbed into the skin, involve the application of corticosteroids to reduce the immune response, and certain lotions to reduce the level of itching or absorb water from sores that form.

Never Going Into the Woods Again. What Does This Have to Do With Mango?

Right, back to mango! It turns out that mangos, along with pistachios and cashews, contain small amounts of urushiol. In mangos, the compound is located mostly in the skin, but it’s also in the fruit that’s closest to the skin once the mango is peeled.

Thankfully, since most of the compound is in the skin, stem, and leaves of the plant, mango-induced dermatitis is most common if picking or peeling a mango, rather than from ingestion.

However, for some people who are extremely sensitive to urushiol, mango consumption, even after it’s been peeled, can sometimes lead to an allergic reaction.

Similarly, much of the urushiol in cashews and pistachios is in the shell, rather than in the nut itself. There’s still enough urushiol in the meat of the nut to cause issues if consumed raw, which is why these nuts are roasted before being eaten (yes, even “raw” cashews are heated to break down the urushiol oil).

For most of us, these safety precautions are enough to keep us from experiencing an urushiol-triggered reaction to mango, pistachios, or cashews. For a few, however, mango consumption — even peeled mangos, or mangos that are blended and served in desserts or other dishes — can be enough to cause itchiness and irritation in the mouth, sometimes called “mango mouth”.

For these individuals, the only course of action is to avoid mango consumption. I’m grateful that I’m not affected — although now that we’re fully working from home, I have to purchase my own dried mango if I wish to keep snacking.