Oak Apple Galls make nice powder puffs, once they are vacated. Another lesser-known use is a wet willy- tickler, as demonstrated by the adventurous Megan Riley.
These are some of the most common galls I see in the southern Appalachians, and can be found growing from various red oaks, such as the Scarlet, Red and Black Oaks (Quercus spp., Fagaceae). These golf -ball sized brown papery growths are home to the apple gall wasp (Amphibolips confluenta), which, contrary to its scientific name and popular wasp folklore, does NOT in fact, resemble a bilingual, frog-mouthed wasp.
Seriously though, the single larva of the gall wasp develops inside this spongy cozy home until it emerges as an adult winged wasp. Once its home is vacated, enterprising woodswomen shake out the larval poop and incorporate the spongy remains into their outdoor beauty regimes.
Galls are formed from plant tissue, in response to chemicals produced by insects, which mimic various plant growth hormones. Inside the gall, the insect(s) happily munch on the plant tissue, while protected from predators. They are formed from various plant tissues depending on the host and the insect involved. If you have the gall, break your cotton-ball habit and get back to your primitive beauty care roots.