We asked Shah if perhaps it is that microbiome , then, that also causes the lint, but, she explains, that while the microbiome inhabitants may be a part of the belly button lint mix, it's not necessarily the cause. Soren White, a board-certified dermatologist based in New York City, says that navel fluff is typically only a problem for people who have innie belly buttons , as fibers can get trapped there.
In addition to the actual shape of your belly button, it also matters how much hair you have, as that's another factor that leads to fibers and debris getting stuck where you may least suspect it.
Nevertheless, regardless of the trajectory of your belly button or the amount of hair that covers it, both White and Shah make a point of noting that, if you regularly cleanse your belly button, the formation is a lot less likely. Over the course of a day—or however long you go without showering —these particles collect into a weird little wad, typically reflecting the color of your clothing.
Depending on your belly button anatomy, you might see some belly button lint every day, or it might be so tucked away that you never really give it a second thought. It all depends on your body. One is the shape of your belly button. The architecture of that indentation, Dr. Such superb hosts, those innies! The deeper and wider your navel is, the more space available for fluff to amass. Having more abdominal fat surrounding your navel also helps to create a deeper cavity for lint build-up, Dr.
Khetarpal adds. You can still get belly button lint if you have an outie, but it might be more crammed into the folds of your skin rather than all together in one place.
The amount of hair on your abdomen also influences your belly button lint. Those who have longer, coarser, and thicker hair on the torso usually wind up with a lot more navel fluff. But sometimes belly-button deposits are no laughing matter.
Soon after Steinhauser published his research, doctors in Nebraska reported a case of a year-old obese woman with a rare condition called omphalitis, or inflammation of the umbilical cavity. She had been bleeding from it for four months. But it turned out to be a ball of lint nearly a centimetre across. They pulled it out, and she was cured. Earwax , or cerumen as doctors call it, is mostly dead skin plus an oily secretion called sebum and a watery one from sweat glands.
People fall into two distinct earwax camps: wet and dry. Wet earwax is orange-brown and sticky; the dry type is translucent and scaly, like dead skin. That is because it is dead skin. A few years ago geneticists discovered that dry earwax is caused by a recessive mutation in a single gene, ABCC Thank you for visiting nature.
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We show that respiratory cycle provides a periodic traction force for the production of belly button lint or navel fluff. The relative motion induced between clothing and skin, during breathing, transports the clothing fibers over the abdominal skin via an asymmetric sliding mechanism effected by the specific orientation of the cuticle scales of body hair. The source of these fibers can be the piece of clothing worn adjacent the navel area or the drying towel used after shower.
The ratchet like topology of hair surface ensures a net unidirectional transport of these fibers. Since the predominant direction of growth of hair in the abdomen is toward the navel, this unidirectional transport leads to a perpetual accumulation of fibers in the navel over the course of the day. By analyzing the force balance on a moving fiber and the transport dynamics of its number density distribution, we develop a mathematical model to describe the accretion rate of lint fibers in the navel.
The online survey gathered further information, mostly qualitative, from the participants regarding BBL. He concluded, among other things, that having sufficient amount of body hair is an essential condition for the production of BBL see Fig. Later, Steinhauser 2 carried out chemical analysis of samples of his own BBL to reveal that its major constituent is textile fibers, confirming the general belief among the public. He also reported the presence of foreign materials such as cutaneous scales, house-dust, sweat, etc.
The average mass of BBL was found to be 1. Note the difference in hair population density around the navel. Note the overlapping cuticle layers. Reprinted from ref. At any rate, these articles did not attempt to perform any analysis of the physical mechanism underlying the phenomenon of BBL formation.
Steinhauser 2 further noted that the scaly structure and the direction of growth of the hairs and normal body movement could play a major role in the dislodging and transport of lint fibers. But finer details of the mechanism and how all these factors lead to a constant driving force for the one-way transport remain elusive. Building upon these ideas, we attempt to model the phenomenon of BBL development by considering the dynamics of transport of textile fibers through the region between the piece of clothing simply referred to hereafter as shirt, but note that it could be a piece of lower clothing as well and skin.
A periodic forcing on the fibers is proposed to be generated via the respiratory cycle. The cuticle scales on the abdominal hair act like small ratchets pointed towards the navel effects.
We model this feature as an asymmetric tribological property of the hair. By solving the one-dimensional transport equation based on a uniform transport rate of the fibers, the accretion rate of lint in the navel is evaluated.
We obtain a reasonable match for the mass of the BBL with the values reported experimentally by Steinhauser 2. Other rarer body movements that could result in high amplitude forcing function e.
However, all these effects are expected to only enhance the transport rate of lint to the navel; hence our results are conservative. Also, designing more efficient lint removers are important in medical field, given that lint contamination during surgical procedures is found to cause post-operative complications 4. Before moving on to the theoretical framework, it is necessary to address its conceptual underpinnings.
First, let us discuss the pertinent morphological features of human hair. A human hair consists of a central core called the cortex covered by a protective sheath of thin cellular layers called the cuticle. As revealed by scanning electron microscope SEM and atomic force microscopy AFM images 5 , 6 of a human hair fiber, the cuticle has a multi-layered structure, which is reminiscent of overlapping roof tiles see Fig.
The cuticle sheets run and overlap longitudinally in a root-to-tip direction along the hair fiber axis. Each cuticle sheet is typically 0. Expectedly, the ratchet-like architecture of hair surface results in a strong directional dependence of the frictional properties of hair. For example, the dynamic coefficient of friction measured in the tip-to-root direction is more than twice that in the root-to-tip direction 5 , 6.
This is expected because the protruding edges of the cuticle scales offer additional resistance to the motion of another surface on the hair surface in the tip-to-root direction. On the other hand, the frictional resistance will be less in the root-to-tip direction. As discussed below, this directional asymmetry plays a pivotal role in facilitating the unidirectional transport of lint fibers. The saw-tooth like topology of hair surface could also be the reason for extricating lint fibers from fabrics through abrasion, when the fabric moves relative to the hair in the tip-to-root direction.
The fabric could be the shirt worn by the individual or the drying towel used after shower. Such dislodged lint fibers present over the abdominal skin finally get accumulated in the navel to form the BBL.
Note that the possibility of drying towel acting as a source of lint fibers is not considered by any of the previous studies, which consider only the shirt worn by the individual as the source. While this could possibly explain the rare cases of discrepancy between the color of BBL and the shirt worn, as we will see later, the contribution from lint fibers of drying towel is very small in the production of BBL. Now taking into consideration the periodic abdominal motion induced by the breathing cycle and the fact that all body hairs in the area around the navel are stooped toward the navel see Figs 1a and 2 , we arrive at a simple physical picture explaining the transport process of lint fibers to the navel.
During the respiratory cycle, the size of the abdomen periodically changes, setting up a relative motion between the skin and the shirt whether loose or tight. Let us focus on the consequences of this motion along the line connecting the navel and the middle of the chest. Similar arguments can be applied to other directions too, but are not addressed here to keep the discussion short.
During the inhale phase of the respiratory cycle, in the upright position of the body, the motion of shirt is upwards relative to the skin see Fig. A cartoon illustrating the sliding motion of a lint fiber in an area superior to the navel. Two consecutive phases of a breathing cycle: a inhale, b exhale are shown.
The spikes on the hair fibers represent the cuticle scale edges. The net effect of the relative oscillatory motion of the fabric, as shown by the red arrow, is to transport the lint fiber toward the navel in a cycle because the hairs point toward the navel. The final initial, respectively location of the lint in each phase is shown by the solid dashed curve. Since the frictional force will be more in the tip-to-root direction the sliding velocity of the lint fiber in the exhale phase shown by the blue arrow is less in the inhale phase than it is in the exhale phase.
Consider a lint fiber dislodged from the shirt that is sandwiched between a hair fiber and the shirt worn by the individual. As the shirt moves relative to the hairs, the lint fiber will tend to move along with shirt.
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