Demodex mites are common in nature, and people are generally susceptible to them. There are two species of Demodex parasites that can infest human skin. Demodex follicularis lives in eyelash follicles, whereas Demodex brevis burrows into meibomian and sebaceous glands of the eyelid.12 Both species Demodex were clearly observed in patients with demodicosis and chalazia. Most patients with demodicosis are asymptomatic mite carriers. Recently, it has been reported that demodicosis was prevalent in cases of blepharitis, and that Demodex mites played an important role in chronic inflammation of the skin, hair follicles, and glands of the eyelid.3 Although the mechanism by which Demodex induce pathogenic damage is unclear, it likely involves direct damage from Demodex mites and their metabolites, delayed hypersensitivity induced by these metabolites, local infiltration of inflammatory cells, and secondary infection of pathogenic microorganisms, especially bacteria.8,13
Chalazia is common in pediatric patients, and presents with multiple and recurrent chalazia. Chalazia exhibits poor treatment coordination and is difficult to prevent. This study showed that Demodex infestation was more prevalent in patients with chalazia than the control group. Furthermore, demodicosis was not found in the control group. Demodicosis is commonly age dependent,11, 14–15,30 with more frequent detection in individuals over 71 years old than in children between 3 and 15 years old.11 This was consistent with the observations that demodicosis was rare in healthy children,11,16−17 and suggesting that Demodex infestation of pediatric patients is a risk factor for chalazia.
Previous studies2,18 commonly used the presence of mites to determine Demodex infection. Even though Demodex mites were counted in some articles, the mite count was not used as the diagnostic criterion. There have not, to our knowledge, been specific studies in children with demodicosis, and the diagnosis and treatment for demodicosis in domestic populations are as follow: 2 mites/3 lashes in each eyelid is suspiciously positive and ≥ 3 mites/3 lashes is definitively positive, requiring clinical treatment11. In addition, Demodex lives in eyelash follicles,meibomian glands, and sebaceous glands.12 Any mites attached to the eyelash root are removed simultaneously when eyelashes are removed for sampling, but it is important to consider that Demodex mites also lay eggs in the eyelash follicle, indicating that there may be more Demodex present than what is observed in the eyelash sample. Because demodicosis is not as common in the pediatric population, and mite count was not consistently correlated with the severity of chalazia,2,6,19,31 presence of Demodex mites should be taken seriously. In our study, demodicosis with 2–3 mites/12 lashes contrived only 9.75% of chalazia patients with Demodex infestation. In pediatric chalazia, microscopic examination for Demodex mites should especially careful to avoid missing a diagnosis. In addition, if there is ≥ 1 mite/12 lashes, it is recommended that the patient be treated as Demodex positive and undergo intervention.
In this study, it was found that Demodex mites were more frequent in patients with recurrent chalazia and those with skin surface involvement. Moreover, ocular demodicosis was significantly more prevalent in patients with recurrent, multiple, and MGD chalazia, which matched the pathogenic role of mites in meibomian and sebaceous glands.13,16,18,20 Our results showed that demodicosis was more prevalent in chalazia patients regardless of blepharitis, similar to previously studies suggesting that demodicosis was associated with blepharitis3–4, 17 and chalazia.2,13, 17–18,20 These results also suggest that Demodex infestation could be an independent risk factor of chalazia after adjusting for the effects of blepharitis.21
Demodex mites often utilize host cells and their metabolites, sebaceous gland secretions, sebum, and keratin as sources of nutrients. Changes in the local microenvironment of the eyelid caused by chalazia are conducive to Demodex parasitism, and demodicosis could worsen the manifestation of chalazia and cause its recurrence.8,13,15,21 This highlights the importance of mite treatment.
Recurrent chalazia is reported in 17–25% of affected children, which is more common than in the adult population.8,22 We observed that only 0.9% of pediatric patients with chalazia required re-operation for recurrence after comprehensive treatment for Demodex infestation. These results suggest that eradication of Demodex may be an effective method for preventing recurrence. Both 2% metronidazole ointment and Tea tree oil are reported as effective alternatives for treatment of Demodex infestation.23 Terpinen-4-ol, which is the most active ingredient of tea tree oil, is currently the treatment of choice for pediatric demodicosis because it has fewer side effects.24,29
Demodex mites typically complete one generation of their life cycle in 14–15 days.8 We recommend comprehensive treatment25 for mites because children are often reluctant to cooperate with treatment. The course of treatment is generally 1 to 3 months, encompassing several Demodex life cycles.26
In addition, ocular discomfort was often difficult to interpret due to difficulty for children to describe the sensation, causing complaints to be overlooked.27 In order to prevent development of demodicosis, it is important for children and their parents to maintain good ocular hygiene, including applying warm compresses and contact-isolation of demodicosis to control ocular Demodex infection.21,28
This study had several associated limitations. Although adult or larvae Demodex were observed, Demodex folliculorum and Demodex brevis were not recorded separately for further study of which species was more prevalent in pediatric demodicosis with chalazia. Sampling the eyelash in the correct places is essential for microscopic Demodex detection, and there may be a non-invasive alternative, such as in vivo confocal microscopy, to sample eyelashes for Demodex detection, which could potentially avoid the failure to remove Demodex completely during epilation. This would also be more conducive to the review of pediatric patients. Since metronidazole gel has been reported to be both effective and safe in the treatment of demodicosis, comparing the effectiveness of different anti-mite treatments may be beneficial.
The majority of chalazia patients, especially those with recurrent and multiple chalazia, suffered more from demodicosis than healthy children. Demodicosis should be considered as a risk factor of chalazia. In children with chalazia, Demodex examination and comprehensive treatment of Demodex mites should be applied to potentially prevent recurrence.