Plastic bag of water: Latin American superstition or science?

[Don’t speak Spanish? No problem! Scroll down for the English translation!]

En un viaje reciente a una panadería mexicana, me di cuenta que habia una bolsa de agua con unos centavitos adentro colgada de la puerta. Al principio pensé que alguien estaba haciendo una broma y que el agua va a caer, pero cuando abrí la puerta, era obvio que la bolsa estaba atada muy segura. Mi segunda sospecha era que la bolsa de agua era resultado de una creencia popular de América Latina o de México – que era una superstición que tienen que ver con la prosperidad o la suerte.

Al salir de la tienda con una bolsa llena de conchas, marranitos y otros panes en la mano, le pregunté a Carlos si sabía algo al respecto. Carlos no estaba seguro, pero también sospechaba que era una creencia popular.

Una vez en casa, investigue para encontrar la respuesta. La repuesta – Esto en realidad no es una superstición cultural, sino cientifica! Resulta que la bolsa de plástico de agua colgada en una puerta es un repelente de moscas. Hay desacuerdo sobre cómo funciona realmente, pero muchos juran que funciona. No he visto ninguna mosca en la panadería mexicana, entonces vale la pena intentarlo. Tal vez ahora nuestras chanclas no tienen que usarse como matamoscas.

A plastic bag of water hangs from the top of a door at a Mexican bakery.


On a recent trip to a Mexican bakery, I noticed a bag of water with a few pennies in it hanging from the door. At first I thought someone was trying to play a practical joke and the water would spill, but when we opened the door, it was obvious that it was tied very securely. My next suspicion was that the bag of water was actually a Latin American or Mexican folk belief or superstition having to do with prosperity or luck.

Leaving the store with a bag full of conchas, marranitos, and other panes in hand, I asked Carlos if he knew anything about it. Carlos wasn’t sure but also suspected it was a folk belief.

Once home, I researched to find the answer. This is actually not cultural superstition, but science! It turns out the plastic bag of water hung on a door is a fly repellent. There is disagreement over how this actually works, but many swear that it does work. I didn’t see any flies at the Mexican bakery, so it’s worth giving a try. Maybe now our chanclas don’t have to double as fly swatters.


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  1. Jamie and I saw the same thing at an Eastern Shore seafood place. We suspected something to ward off evil . . . actually that is kind of correct . . . those flies are evil!

  2. As soon as I read your post…I thought of that seafood place. I thought it was voodoo because the guy working had a very strong creole accent. There weren’t any flies there though!

  3. Hola :) Yo en algún lugar si habia escuchado/visto lo de la bolsa de agua para espantar las moscas,pero no estoy segura si lo vi en Nicaragua o Republica Dominicana. I had never seen it inside a store though…will have to try it for sure :D
    This week PinkGuayoy is also participating in Spanish Friday, here is the link:

    Have a great wiken :D

    • Qué interesante! I wonder where this “invention” originated.

      Gracias por participar en Spanish Friday. Voy a visitar y comentar en tu blog este fin de semana!

    • That’s cool (el vaso de agua) … Thanks for leaving your link, Tara. Can’t wait to see what locuras you’re up to now ;) I’ll be sure to visit and comment later this weekend!

  4. Siempre tan util con los consejos, hermana! jajaja… I was thinking it was for good fortune and was already planning to put my little bolsita ful of pennies at the front door :-) Oh well, but as a fly repellent… I guess, maybe I’ll try it out. sigh.

    • LOL – How about it’s for good luck *AND* it repels flies? :)

      If you want buena suerte, Carlos says to put magnets somewhere near the door.

  5. Interesante! Lástima que las moscas no hablan para preguntarles qué onda, que por que la charamusca colgante les da tanto pánico!
    No habrá algo para evitar que la gente chismosa y malandra entre a tu casa? If you EVER find out… let me know (jijiji)

    • LOL – voy a decirte un remedio para que la gente chismosa no entra a tu casa si me das un repelente de Suegras. jajaja ;)

  6. Tracy, you are a lifesaver! I was just about to Google “natural fly repellent” or something like that because the flies have arrived by the hundreds and they don’t look like they’ll be leaving soon. I can’t believe I had forgotten all about the water in a plastic bag. You see them at all of the different food puestos here in town. I’m putting some up as soon as I post this comment. I’ll let you know if it works. :)

    • I love when I coincidentally run into things online that I actually had on my “to do” list to figure out. Let me know if this works well for you!

      I’ve had a bag of water with 2 pennies in it hanging from our back door for 2 days now and it’s REALLY WEIRD – we haven’t had any flies come in the house! We usually get one every time we open that door to let the dog out.

  7. Yes, here in El Salvador you see little bags of water hanging all over the place! Mostly at outdoor food stands. The theory that people have explained to me here is that the water and the plastic (and the pennies, in cases when they´re used) cause reflections of light, which cause the flies not to come near. The effect doesn´t have a super wide radius, but at least it keeps the flies away from the food under the bags. On mobile food carts or canopies at a fair, there will be several bags hanging from the beams. Just be careful not to bump your head! =)

    • From now on, when buying my Mango Twist, Minuta etc etc I’ll be looking for the plastic bag with water. Never seen it before but your explanation makes total sense. Flies have like 2 million eyes (OK, maybe not that many) so can you believe how crazy they might feel with that weird reflection!

  8. That’s just plain bizarre. I’ll have to keep an eye out for these bags. Can’t recall ever having seen one.

  9. This was such a funny post Tracy, but now I am considering taking a trip to our local panaderia, I love their conchas! It seems I’m always learning more about my husband’s superstitious behavior, and now… my own, I don’t even realize I’m doing it sometimes.

    • Cristina – Enjoy the conchas! This bakery I went to makes amazing ones – they were soft with just the right level of sweetness and a very slight hint of citrus.

  10. Ha! I really thought you were going to say para las malas vibras. My parents have a garlic bunch for the vibes, so I’m sure they will love to hear about this water bag! Makes me want to try it in my apartment hmm wonder where I would put it? Thanks for sharing!!

    • I put a bag on my back door but not one on the front door. I don’t want the neighbors to see. LOL. What will your apartment neighbors think?

  11. Jajaja. En la Argentina usamos the same method!!
    Además, también se acostumbra poner transparent plastic bottles filled with water, para ahuyentar a perros y gatos, so they won’t damage your garden. Jijiji

    • How cool to know this is done in Argentina! I wonder if the bottle of water would work for flies. It would be easier to tie up than the bag. I got a bag of water hanging but it took a lot of tape. LOL

  12. I’ve seen the plastic bags here in Chile too, but usually empty (partially filled with air) and definitely without the coins. I always thought it had something to do with the movement because the empty bag flutters with the slightest breeze— but your version is weighted, so what the heck is going on here? People DO swear it works… and I’ve never seen any evidence to prove them wrong!

    • In Chile too! This is awesome.

      My bag of water is working well, but it was heavy and difficult to hang. Maybe I’ll try the bag of air to compare and see if it works just as well.

  13. Siendo latinoamericana hasta la medula jamas lo habia visto ni oido, me parece genial la idea de no tener que usar insecticida. Me encanto el post ;)

  14. Loved this post amiga! Yes, we love our plastic bags with water here in Mexico! LOL! The theory says that water makes the reflection of the flies seem like they are huge terrible creatures so they stay away from “it”… when it´s really just themselves! Thank goodness they are not smart! jajajaja!!!

  15. I really don’t think the bags with water do a darn thing, pennies or not, judging by my experience in my husband’s hometown, hordes of flies getting on stuff despite little baggies hanging right there. But at my house I still hang up the little baggies with water and pennies all over the place outside whenever we have a party, because I don’t want to hear it. “Hubieras colgado unas bolsas con agua…”

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