We have always been told that we are mainly composed of cells that form tissues, that these tissues form organs, and these organs constitute systems. However, our body is much more than a set of eukaryotic cells, since populations of thousands of bacteria live in it, as well as other living beings such as the protagonist of this article: a “worm” that can live in your eyes and other parts of your face.
A tiny mite that on your eyelashes
Despite its worm-like appearance, the organism we are talking about today is not a worm , but a mite of the Demodex genus, a genus in which we find more than a hundred different species , of which two are the most studied and were the first to be discovered: Demodex folliculorum and Demodex brevis .
Our face is the city inhabited by these animals, the neighborhoods through which they move are the different parts of our face where there are abundant sebaceous glands and secretions (nose, cheeks, lips, forehead, chin), although the busiest are the eyelashes . In these neighborhoods they establish their homes in the main streets, the pores and the hair follicles .
Before you get up to look in the mirror to try to find one of these animals, we inform you that Demodex cannot be seen with the naked eye , as their size is between 0.2 and 0.5 millimeters . But don’t worry, although you can’t see it in the mirror, you should know that this mite is not in all of us, since its presence is more likely the older our age. Also, if they do inhabit your eyes, they are not always harmful .
Demodex feed on our dead skin
It may seem like a sad way of life to depend on another organism in order to survive, but nothing is further from the truth. In nature there are thousands of examples of animals that have a commensal or parasitic relationship with their hosts. In this case, the Demodex are ectoparasites – parasites that are found on the surface of our body – and their way of life is really interesting, both from a biological and clinical point of view.
Inside our pores and hair follicles, they live by feeding on our secretions and dead skin . In their body they have structures that allow them to “scratch” dead cells and feed on them.
Each hair follicle is a home for the Demodex mite
Like all living organisms, the mites in your eyes have a reproductive function. They can lay between 20 and 30 eggs in a hair follicle and their reproductive cycle lasts approximately 14-18 days .
On the surface of the follicle, where the mites live in their adult state , female Demodex are inseminated. After copulation, they move into it near the sebaceous glands to lay eggs.
Once they emerge from the eggs, the larvae adhere to the interior of the follicle until they grow, transforming into a protonymph, the next phase. Before reaching its adult state, the protonymph goes through another phase, that of deuteronymph. It is at that moment when the mite in its most advanced juvenile phase decides to move towards the surface of the follicle, where it will reach the most mature stage of its life cycle, becoming an adult. Upon reaching its adult state, the mite decides to become independent and look for another home to settle in. In his case, the best home is a new follicle to go to find food and start a new family.
Are eye mites dangerous to our health?
Under normal conditions, the Demodex mite is not harmful to health . In fact, as we have already mentioned, they are dedicated to feeding on our dead cells and sebum. However, like other living beings that inhabit our body, there are certain cases in which this mite can cause damage and skin disorders.
The skin is the organ that protects us, and the damage that is generated in it can open the door to different pathogens – such as viruses or bacteria – that can be harmful to our health. Demodex may be one of the key masters that opens those doors allowing these pathogens to enter us.
In addition, an excess of these mites in a single follicle can cause other inconveniences on the face such as conjunctivitis, inflammation and have even been linked to other types of conditions such as rosacea, a skin disease in which redness occurs . There is also in the scientific literature a relationship between these mites and eye problems such as dry eye or blepharitis (an inflammation on the edge of the eyelids).
How to remove mites from eyelashes?
Treatments to reduce the number of these parasites under harmful conditions are directed at the use of compounds with antiparasitic properties in addition to maintaining adequate hygiene .
Recently, a study carried out at the Ocular Microsurgery Institute (IMO) showed that there is a greater presence of this mite in patients with basal cell carcinoma , a common malignant tumor that affects the eyelids. However, its relationship with this tumor and with other types of diseases is still unclear. For this reason, today, research continues to be carried out on this ectoparasite and its relationship with possible conditions of the skin and, mainly, of the eyes.
References:
Cheng, A. M., Sheha, H., & Tseng, S. C. (2015). Recent advances on ocular Demodex infestation. Current opinion in ophthalmology, 26(4), 295-300.IMO. 2019. Demodex, el “habitante” desconocido de las pestañas.Rufli, T., & Mumcuoglu, Y. (1981). The hair follicle mites Demodex folliculorum and Demodex brevis: biology and medical importance. Dermatologica, 162(1), 1-11.Nicholls, S. G., Oakley, C. L., Tan, A., & Vote, B. J. (2017). Demodex species in human ocular disease: new clinicopathological aspects. International ophthalmology, 37(1), 303-312.Zhang, A. C., Muntz, A., Wang, M. T., Craig, J. P., & Downie, L. E. (2020). Ocular Demodex: a systematic review of the clinical literature. Ophthalmic and Physiological Optics, 40(4), 389-432.
