What would happen if you ate one of those silica gel packets?

iStock/bymandesigns
iStock/bymandesigns

Well, for one thing, you'd be eating a misnomer. Silica gel isn't actually a gel, but a granular form of silicon dioxide (SiO2), a compound formed when silicon is oxidized.  Silica gel is synthetic but SiO2 is also commonly found in nature (I trust you've heard of sand and quartz.)

But before we discuss the consequences of ingestion, here's a quick history lesson. Silica gel has been around since at least the 1600s, but was a scientific curiosity until its absorbent properties were put to use during World War I in gas mask canisters. Walter Patrick, a chemistry professor at Johns Hopkins University, patented silica gel in 1919 and joined with Grace Davison, a Maryland-based chemical company, to further develop it. Davison began selling silica gel in 1923 but it didn't take off until World War II.

Silica gel can absorb a lot of water—about a third of its weight—without undergoing a chemical reaction or changing shape. Even when they're saturated, the granules stay dry to the touch and can be reused after heating at 250 °F for two hours. These properties make silica gel extremely useful for controlling moisture and humidity, and during the war it was used to keep medicine, military equipment and supplies dry.

Today it's packaged with leather products, pepperoni, electronics and vitamin pills and used in museums and libraries to guard against rust, corrosion, tarnishing, mildew, mold and spoilage.

Risk Assessment

So what happens if you decide to defy the warning on the packet, defy the social norms of polite society and munch on a few granules? I hate to be anti-climactic, but most likely, the answer is "¦nothing! (Of course, there are some caveats, which we'll get to in a minute.)

If you think about it, silica gel is basically man-made sand. It's non-toxic and chemically non-reactive. People who have eaten anywhere from a few beads to a whole packet have reported no ill effects. If you're curious, it's reportedly almost tasteless, like licking a postage stamp.

Why the Skull & Crossbones?

Why the warnings, then? Well, silica gel isn't completely dangerous, but it isn't completely safe. Here are a few reasons the packets come with stern warnings:

Dehydration "“ Silica gel's job is to absorb moisture, and it's going to keep doing that as you digest it. You'd have to eat an awful lot of it to dehydrate yourself, but if you did, it would dry you out in no time.

Silicosis "“ This lung disease, also called Grinder's disease and Potter's rot, is caused by inhaling silica dust and causes symptoms like scarring and nodular lesions in the upper lobes of the lungs, shortness of breath, fever, and cyanosis (blue tinted skin).

Foreign vapors and toxic additives "“ You don't know what the silica gel was exposed to between Point A and Point B. Eating a packet that came in a box of cockroach traps is definitely not recommended, but the gel could have absorbed other nasty stuff during manufacture or shipping and absorbed it. Sometimes, these things are added intentionally and packaged silica gel might have a bit of fungicide or pesticide added to it.

Another additive to watch out for is cobalt(II) chloride, which is toxic. This is added to the gel when a visible indication of absorption is needed. The cobalt(II) chloride makes the granules blue when they're dry and turn pink when they're saturated.

And the biggest reason? Lawsuits! "“ Even if the contents of a packet are plain old silica gel with no cobalt(II) chloride, and there's no silica dust present and there aren't enough granules to cause dehydration, companies have been sued over far stupider things. They're just covering their butts.

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How Is a Sunscreen's SPF Calculated?

Rawpixel/iStock via Getty Images
Rawpixel/iStock via Getty Images

I’m a pale person. A very pale person. Which means that during these hot summer months, I carry sunscreen with me at all times, and apply it liberally. But I’ve never really understood what those SPF numbers meant, so I asked some sun care to break it down for me—and to tell me how to best apply the stuff so that I can make it through the summer without looking like a lobster.

Soaking up the sun ... safely

SPF stands for Sun Protection Factor, and it indicates a sunscreen’s ability to block UVB rays. The concept was pioneered at the Coppertone Solar Research Center in 1972; in 1978, the FDA published an SPF method based on Coppertone’s system, according to Dr. David Leffell, chief of Dermatologic Surgery and Cutaneous Oncology at Yale.

The numbers themselves stand for the approximate measure of time a person who has applied the sunscreen can stay out in the sun without getting burned. Say you get burned after 20 minutes in the sun without sunscreen; if properly applied (and reapplied), SPF 30 will allow you to stay in the sun 30 times longer without burning than if you were wearing no protection at all. So, theoretically, you should have approximately 600 minutes, or 10 hours, in the sun. But it’s not an exact science because the amount of UV light that reaches us depends on a number of factors, including cloud cover, the time of day, and the reflection of UV rays off the ground, so it’s generally recommended that you reapply sunscreen every two hours (or even sooner).

What gives a sunscreen a higher SPF comes down to the product’s formulation. “It’s possible that an SPF 50 might contain slightly more of one or more sunscreen active ingredients to achieve that higher SPF,” Dr. Patricia Agin, president of Agin Suncare Consulting, says. “But it’s also possible that the SPF 50 might contain an additional active ingredient to help boost the SPF performance to SPF 50.”

No matter what SPF your sunscreen is, you’ll still get a burn if it’s not properly applied. So let’s go over how to do that.

How to apply sunscreen

First, make sure you have a water-resistant, broad spectrum sunscreen—which means that it protects against both UVB and UVA radiation—with an SPF of at least 30. “Typically, you don’t have to buy sunscreen that has an SPF higher than that unless you have very sun sensitive skin,” Leffell says. “That’s a very small percentage of the population.” (Redheads, people with light eyes, and those who turn pink after just a few minutes in the sun—you’ll want to load up on SPF above 30.)

Twenty minutes before you go out to the beach or the pool, begin to apply your sunscreen in an even coat. “Don’t apply it like icing on a cake,” Leffell says. “I see these patients and they’ve got the tops of their ears covered with thick, unevenly applied sunscreen, and that’s not a good sign.” Sunscreen sprays will easily give you that even coat you need.

Whether you’re using lotion or a spray, when it comes time to apply, Leffell recommends starting with your scalp and face, even if you plan on wearing a hat. “Make sure you’ve covered the ears and nose and under the eyes,” Leffell says. “Then, I would move down to the shoulders, and make sure that someone can apply the sunscreen on your back beyond the reach of your hands.”

Other areas that are important that you may forget to cover, but shouldn’t, are the tops of your feet, the backs of your hands, and your chest. “We see it all the time now—the v of the chest in women has become a socially and aesthetically huge issue when they are 50 and beyond. Because even though they can treat their faces with all sorts of cosmetics and procedures, the chest is much harder, and they are stuck with the face of a 40-year-old and the chest of a 60-year-old. You want to avoid that using sunscreen.”

Another important thing to keep in mind: Water-resistant doesn’t mean waterproof. “I always tell patients to reapply every couple of hours while you’re active outdoors," Leffell says, "and always reapply when you come out of the water or if you’ve been sweating a lot, regardless of whether the label says water resistant."

Determining whether or not you’ve succeeded in properly applying your sunscreen is easy: “You know you’re applying your sunscreen properly if, after the first time you’ve used it, you haven’t gotten a burn,” Leffell says.

Agin has a caveat, though: "It’s not a good idea to think of sunscreens only as a way to extend your time in the sun," she says. "One must also understand that even before becoming sunburned, your skin is receiving UV exposure that causes other damage to the skin. At the end of the 600 minutes, you will have accrued enough UV to cause a sunburn—one Minimal Erythema Dose or MED—but there is pre-MED damage done to skin cells’ DNA and to the skin’s supporting structure of collagen and elastin that is not visible and happens even before you sunburn. These types of damage can occur without sunburning. So you can’t measure all the damage done to your skin by only being concerned about sunburn."

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us atbigquestions@mentalfloss.com.

An earlier version of this post ran in 2014.

What's the Difference Between Ice Cream and Gelato?

iStock/Getty Images/zoff-photo
iStock/Getty Images/zoff-photo

'Tis the season for beach reads, tan lines, and ice-cold desserts. You know it's summer when going to the local ice cream or gelato shop becomes part of your daily routine. But, what exactly is the difference between these two frozen treats?

One of the key differences between the two is butterfat. While ice cream's main ingredients include milk, cream, sugar, and egg yolks, the secret to making gelato is to use much less cream and sometimes little to no egg yolk. This leads to a much smaller percentage of butterfat in gelato. The FDA rules say that ice cream cannot contain less than 10 percent milkfat (though it can go as high as 25 percent) while gelato, much like soft serve, stays in the 4- to 9-percent range.

The churning method for both also differs, which affects the treat's density. Ice cream is churned at a much faster pace, leading to more air being whipped into the mixture. Ice cream's higher butterfat content comes into play here—due to all of that milkfat, the mix absorbs the air more readily. Gelato, on the other hand, is churned at a slower pace and absorbs far less air, creating a much denser dessert.

You also might have noticed that the serving style for the two treats aren't the same, either. In order to get those perfectly stacked ice cream scoops on a cone, buckets of ice cream must be stored at around 0°F to maintain its consistency, while the softer gelato is stored at a warmer 10°F to 22°F. Ice cream is then scooped into fairly uniform balls with the round ice cream scooper, whereas a spade or paddle is best for molding gelato into mound in a cup or a cone.

You can't really go wrong with either gelato or ice cream on a sweltering summer day, but there is one more difference to keep in mind while you debate which to get: taste. If you want a bolder flavor, you'll want to go with gelato. Because of the density of the cream and because there's less butterfat to coat your taste buds, gelato can seem to have more intensity to its flavors.

Have you got a Big Question you'd like us to answer? If so, send it to bigquestions@mentalfloss.com.

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