What Do Cashews, Mangoes, Poison Ivy and Lacquered Furniture Have in Common?

When you think about your last encounter with infamous irritating plants, such as poison ivy, poison oak or poison sumac, you probably don’t picture yourself enjoying a ripe, juicy mango or crunching down on some tasty cashews and pistachios. All of these things, however, contain a chemical called urushiol. This chemical is responsible for many of the positive and negative characteristics that we associate with some of our most useful and annoying plant neighbors in the Anacardiaceae family.

In its most common state, urushiol takes the form of an oil. When this naturally occurring compound comes into contact with human flesh, however, it can cause severe allergic reactions. These interactions are responsible for the burning sensations, blisters and rashes that many people experience after touching poison ivy. Some sensitive individuals may even report adverse reactions when they eat foods like cashews.

One of the most interesting aspects of urushiol is that even though it’s such a notorious allergen, it actually has valid uses, and we’re not talking about irritating your worst enemies. In traditional furniture-making practices, artisans harvest raw urushiol sap from a special tree to produce urushi lacquer. They then apply this lacquer to wooden furniture with brushes. By curing each layer over time and polishing them repeatedly, furniture makers can create works with amazingly beautiful, high-gloss surfaces. The lacquer’s gradual hardening characteristics also help protect the wood furniture from damage during use.

Even though properly made urushi furniture isn’t dangerous, some people may still experience contact dermatitis outbreaks from touching poorly cured pieces. Of course, this doesn’t mean that you should toss all of your classic Asian heirlooms in the trash, but it’s worth thinking about the next time you come down with an unexpected rash after a weekend of lazing around in your favorite naturally lacquered chair.

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