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J Clin Med Res. 2010 Aug 18;2(4):172-6. doi: 10.4021/jocmr391w.

Hydroscopic properties of organic objects that may present as aural foreign bodies.

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University of Washington School of Medicine, Seattle, WA, 98195, USA.



Organic foreign bodies swell when irrigated with water, potentially making extraction more difficult. As the degree and rate of swelling of different types of organic foreign bodies has not been established, we aimed to analyze the hydroscopic properties of different organic foreign bodies in body temperature water.


Dry kidney beans, brown beans, peas, popcorn kernels, and dried fruits were soaked in a body temperature (37C) water bath. Volume of these organic materials was measured hourly to 8 hours, then at 12, 16, 24, 28, 36 and 48 hours.


All dried fruits and beans increased in volume over time. The volume increase from baseline at 6 hours was between 43% (popcorn kernels) and 383% (kidney beans). Peas, popcorn, and raisins did not increase volume further after 6 hours. Kidney and brown beans had the greatest increase in volume overall (1268% and 482% respectively), and the greatest continued increase after 24 hours.


Many organic substances that frequently present as aural foreign bodies may swell enough in water to lodge tightly in the ear canal. Typical popcorn kernels and dried peas will not swell sufficiently to lodge tightly in the ear canal of a typical child one year or older. A retained organic foreign body in a moist ear canal may cause inflammation until the foreign body can be removed. These risks may be offset by the advantages of successful removal with irrigation.

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