Have you ever played with scratch and sniff stickers? They’re not as common as they used to be. If you ask your parents, they probably remember playing with them all the time when they were young.

Scratch and sniff technology can be applied to all sorts of things other than just stickers, including clothing, compact discs, postcards and advertisements. Scratch and sniff technology involves treating an object with a microfragrance coating.

When the coating is scratched, it releases fragrance molecules into the air that you can smell. The coating usually includes an image related to the fragrance it carries. For example, a scratch and sniff sticker might feature a picture of a banana. When you scratch it, you can smell a banana as if you had just peeled one!

Scratch and sniff stickers first became really popular in the late 1970s. They were fun to put on school notebooks and clothing. Advertisers started to use the technology, too. For example, many perfume makers began to use scratch and sniff technology to coat cards to insert into magazines to promote their fragrances.

Scratch and sniff technology actually has some practical uses beyond just fun, though. For example, some utility companies use them to help people understand what a gas leak would smell like. Researchers use the technology today to help test patients who may be at risk for Alzheimer’s disease, since one of the earliest symptoms is a loss of the sense of smell.

If you’re wondering how they get smells to release upon scratching a coated surface, the secret is a process called microencapsulation. Smells — whether natural or created with chemicals — are captured in the form of molecules that must be distilled into tiny bubbles of liquid.

These bubbles are then microencapsulated in a secret process that turns them into ink-like goo that can then be printed onto stickers and other objects. When the object is then gently rubbed, the microencapsulated bubbles break easily and release their smells. Microencapsulation technology allows the trapped smells to last for years and years.

22 Join the Discussion

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  1. I think tomorrow’s WONDER will be about uncooked meat! I didn’t particularly like today’s WONDER, but then again, it’s 9:30 in the morning…


    • Super guess, Emily! We are always WONDERing with us- how GREAT! We are sorry to hear that today’s Wonder wasn’t your favorite, but perhaps sleepiness got the best of you! We hope you have a SUPER day– we can’t wait to WONDER with you again! :)

    • Thanks for WONDERing with us, Zach! We are THRILLED that you learned something new about scratch and sniff– it’s quite scientific! Thank you for posting a comment– we hope you have a WONDERful day! :)

  2. Hi Wonderopolis,

    That is very interesting I didn’t know that is how Scratch and Sniff work. Thank you for today’s WONDER.

    From Maddi and Lane

    • WOW, what a great comment, Maddi and Lane! Thank you for WONDERing with us today! We’re SUPER HAPPY we could all learn something new! :)

  3. Back at my school, there is a library which has a lot of books. There is a person called Mr. Brian, he is a librarian, and if you’re nice he gives you a scratch and sniff bookmark. :-)

    • Mr. Brian sounds like a WONDERful person, Carlos. We love to read and are so glad that you do, too! We hope you’ve enjoyed learning and WONDERing with us! Thanks for joining– you ROCK! :)

  4. I think that it was a really interesting wonder because I did not know that that was how you work Scratch and Sniff.

    From Michael

    • Way to go, Michael! You’ve learned something new about the science of Scratch and Sniff! We think it’s AWESOME to Wonder– thank you for joining us today! We hope you have a WONDERful day! :)

  5. Interesting. I have a question: why can’t you whistle in outer space? I think it’s because of the lack of air or it could be the lack of gravity.

  6. Hi Wonderpolis,
    Today’s wonder was very interesting! I didn’t know how the “Scratch and Sniff technology” works. I thought it was quite cool to make a puzzle (question) book including Scratch and Sniff answers. I wonder when did the SUPER technology stop? P.S – and why?

    • What a WONDERful thing to hear, Sophie! We are SUPER excited that you enjoyed WONDERing about scratch and sniff technology. :) Different manufacturers still use the technology for different purposes– we WONDER if you’ve found the scratch and sniff technology– or smelled it– on any of your back to school supplies? :)

    • You are a super Wonder Friend, Athenamarie! We love having you here to Wonder with us– thanks for your AWESOME comment! :)

  7. I thought that today’s wonder was very interesting! I was actually just wondering that today! I think one other creative way that scratch and sniff could be used is on hand soaps, candles, etc, because people are always wanting to know what the product they buy will smell like. If companies stuck a simple scratch and sniff sticker on the product, the customer could be sure that they like the scent of the product they buy before bringing it home and possibly being unsatisfied!

    • We LOVE your creative suggestions on how to use scratch and sniff, Gracie! You are off-the-charts AWESOME and we love your SUPER ideas! Thank you for sharing your comments with the Wonderopolis community– we love to have great Wonderers like you! :)

  8. Room #112 I think this story was interesting because it’s just talking about how do scratch and sniff work. Also I never knew or tried to sniff- some work that’s why it’s so interesting to me. Sincerely aisia 112

    • Hello, Aisia in Room #112! We’re so glad you’re here today! We LOVE to learn with great Wonder Friends like you! We hope you enjoyed thinking about all science that goes in to creating a scratch and sniff piece… we Wonder if you have a favorite scent? :)

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Have you ever wondered…

  • How does scratch and sniff work?
  • Does scratch and sniff technology have practical uses?
  • What is microencapsulation?

Wonder Gallery

Try It Out

Ready to exercise your imagination? What other uses can you think of for scratch and sniff technology?

Sure, scratch and sniff stickers are fun, but could they be used in new and creative ways? What about a vacation brochure for a beachfront resort that you could scratch to smell the ocean? Or how about a menu that you could scratch to find out what a particular dish smells like?

What other creative ideas can you come up with? Share your ideas with your Wonder Friends by posting them on Facebook. We can’t wait to read your fantastic ideas!

Still Wondering

ReadWriteThink’s Describe Your Apples reproducible prompts students to describe an apple by listing words that describe how the apples look, feel, sound, smell and taste.

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