Mites (demodex mites)
Which type of mite?
Mites on human skin
Risk factors for demodicosis
Symptoms of mite infestation
Catching a mite infestation - transmission
Prevention / remedies / cures / treatment for mites
References
Which type of mite?
Three different types of mites commonly infect humans:
- Demodex mites
- Scabies mites, which are closely related to the mites which cause mange in dogs and other animals. Sometimes the mites from a dog, cat or bird can pass to humans and cause serious serious itching, rashes and lesions. Scabies mites live predominantly on animals but can also infect humans. They don't normally complete their life cycle in humans, but when they do they can make for intensely itchy nights.
- Bird mites causing the sensation of crawling on the skin, especially at night. They are also virtually impossible to get rid of without tackling their source (the bird's nest).
- A fourth type of mite, dust mites, live in dry dust and debris on the floor, in furnishings, in clothing, in carpets, in bedding, mattresses, pillows and anywhere where fine skin flakes and particles can accumulate. Dust mites do not infect humans and live in human skin or on humans. However their droppings and excretions certainly can affect our health, normally through our lungs and through being allergic to their excretions. Most commonly, dust mites are a trigger for asthma.
It is very important to identify which type of mite you have, because their treatments are different. Incorrect treatment will result in ongoing infection.
Mites on human skin
There are about 65 known species of demodex mites. Only two of those species have been identified as regularly living on humans: demodex folliculorum and demodex brevis. Demodex canis lives predominantly on domestic dogs, but can occasionally infest humans.
Demodex mites live in hair follicles and sebaceous (oil) glands on the skin. Sometimes they are known as eyelash mites. Both species are primarily found on the face near the nose, the eyebrows and eyelashes. They also occur elsewhere on the body, such as in and around the ears, in ear wax, on the scalp, and in skin folds.
Demodex folliculorum mites live in the hair follicles. The adult mites are between 0.3 mm and 0.4 mm long, with a semi-transparent body. You can see fully grown adults with the naked eye, but a microscope is useful for a more reliable examination.
Demodex brevis live in the sebaceous glands connected to hair follicles. The adult mites are up to 0.2 mm long, with a semi-transparent body. You need a microscope to examine a plucked hair or thick oil squeezed from a gland to check for infestation.
The mites eat skin-cells, hormones and oils (sebum) which accumulate in the hair follicles. Their digestive system is so efficient and results in so little waste that they have no excretory orifice.
At night they leave the hair follicles and come out to mate. The eggs are laid 15-20 days after mating, and the legged larvae hatch 3-4 days after the eggs are laid. It takes about a week for the larvae to develop into adults. The total life span of a demodex mite is about two weeks. The dead mites decompose inside the hair follicles or sebaceous glands. Eggs are laid deep in the hair follicles or oil glands, and are impossible to wash out. If you are one of the rare people who have a mite infestation (see below), you have to wait for them to hatch, and then treat the mites. Mite treatment must last 12 weeks.
The optimal temperature for D. folliculorum and D. brevis mites to develop is 16-20 degrees C. Temperatures below 0 degrees C and above 37 degrees C are harmful to the mites. A temperature of 54 degrees C can kill mites, if the temperature is raised to 58 degrees C it effectively kills them all. (4)
Beneficial? You may expect that mites' eggs, clawed legs, spiny mouthparts, salivary enzymes, and particularly their decaying bodies after they die in a follicle, could all provoke an immune response, but this generally doesn't seem to happen. It is likely that they have a beneficial effect by eating bacteria or other micro-organisms in the follicles. Dr Alejandra Perotti from the University of Reading says we should be "grateful" to offer mites a home and have such an intimate relationship with them. "There's nothing to be concerned about having them. They clean our pores and keep them flat. Be happy you have a small microscopic creature living with you, they don't do any damage", she says. (9)
Catching a mite infestation - transmission
Most humans acquire mites shortly after birth, usually during breast feeding, and they form part of the normal commensal skin faunae for the rest of their life. (1) At first there are only a few mites, but during adolescence when the prolific sebaceous glands produce more food for the mites, the mite population can increase. The number of mites on everyone's skin increases with age. (2) About a third of children and young adults, half of adults, and two-thirds of elderly people carry mites. (3)
Mites usually only come out of their follicles at night, as they try to avoid light. They move very slowly, about 1 cm (half an inch) per hour. Mites transfer between people by skin and hair contact, particularly by sleeping with a person in close contact at night. Demodex canis resides deep in the dog's skin, transmission from one animal to another is usually only usually possible with prolonged direct contact, such as mother-to-pup transmission during suckling.
Demodex mites can only live for a couple of hours away from their host in a dry environment. In a wet environment like a damp towel they can survive for longer. They can live for up to 58 hours in a drop of edible oil, and perhaps even longer in an animal fat that resembles the sebum from a sebaceous gland.
This means it is possible to catch a demodex mite infestation by sharing recently-used towels and bedding. However, a good airing in the sun or a cycle in the tumble dryer would make it virtually impossible to transmit an infection. It also means that you cannot get an infection from chairs, carpets, furniture etc.
Risk factors for demodicosis
For the majority of people, mites cause no symptoms (the mites are commensal). (1) It seems that in older people, those with suppressed immune systems (caused by stress or illness), or possibly those taking antibiotics or with compromised skin faunae, the mite population can sometimes dramatically increase and get out of control. Studies show that mite infestations are more common in people with HIV, children with leukaemia, or patients on immunosuppressive drugs. Men are more prone to mite infestation than women because they have more sebaceous glands which provide food for the mites. (2)
Another study (5) of people with chronic demodicosis found that they were more likely to have other chronic diseases and a stressed immune system.
33% of them had chronic renal failure (kidney disease).
27% of them had hypertension (high blood pressure).
25% of them had cancer.
24% of them had hypothyroidism. Other studies (6, 7, 8) show that hypothyroidism (weak thyroid)is often associated with chronic demodicosis.
22% of them had hepatitis B.
19% of them had diabetes mellitus.
Symptoms of mite infestation
The infestation causes a condition known as demodicosis or mite bite, characterised by itching, inflammation and other skin disorders. The "insects under the skin" feeling is known as formication.
- Rosacea.
- Blepharitis (inflammation of the edge of eyelids).
- Large pores.
- Dilated veins.
- Redness.
- Thin hair.
- Adult acne.
- Blackheads.
Acarophobia is the fear of mites and other microorganisms that cause itching. People with acarophobia respond well to "getting away from it all", particularly a relaxing vacation with lots of bare skin exposure at a sunny beach. A follow-up examination of their follicles after the holiday usually shows some level of infestation remaining, but the bright light, boost to vitamin D, natural salt water, reduction in stress and boost to the immune system are usually beneficial.
Prevention / remedies / cures / treatment for mites
Demodex brevis mites live deep in the sebaceous glands and don't come to the surface as often as Demodex folliculorum. This means D. brevis are more difficult to eliminate. Their ovum and nymphs reside deep in follicles and are covered with a membrane which nothing (including pesticides, tea tree oil and antibiotics such as ivermectin) can penetrate. The time from mating until a new generation hatches is 15-20 days, so it is essential to treat an infestation over a couple of cycles to catch the adults and prevent them from mating again. I recommend a three month treatment period, because you have to assume that you have a D. brevis rather than D. folliculorum infection.
Chronic mite infestations are associated with several chronic diseases, in particular a weak thyroid, kidney disease, diabetes, high blood pressure and hepatitis. Do all you can to strengthen your immune system, and your health in general. When you treat these other diseases, you may find the chronic mite infestation will disappear on its own.
- Mites are highly sensitive to light, especially ultraviolet light which kills them. My webpage Vitamin D and sunlight explains how to get the most effective UV light, and why midday sun, NOT morning or evening sun, creates vitamin D. A relaxing break with the skin exposed to just a few minutes of summer midday sunlight is an effective cure for a mite infestation.
- Sauna, as hot as you can take it (or a hair dryer, see in the visitors comments). (4) In addition to killing mites, saunas and hot bath soaks also stimulate your immune system, help you to relax, provide and antioxidant effect, and provide protection and recovery from mite infestation.
- Flowers of sulphur.
- Borax.
- Relaxation with plenty of sleep every day, to build a strong immune system.
- Tea tree oil.
- Clove oil.
- Iodine. A weak thyroid is often associated with demodicosis. Before taking iodine, ensure you have a weak thyroid rather than a overactive thyroid.
- See Grow Youthful visitor's experience with mite remedies.
References
1. Albert M Kligman, Michael S Christensen.
Demodex folliculorum: Requirements for Understanding Its Role in Human Skin Disease.
Journal of Investigative Dermatology (2011) 131, 8-10. doi:10.1038/jid.2010.335.
2. Dirk M. Elston.
Demodex mites: Facts and controversies
2010. Clinics in Dermatology 28 (5): 502-504. doi:10.1016/j.clindermatol.2010.03.006. PMID 20797509.
3. H. G. Sengbusch & J. W. Hauswirth.
Prevalence of hair follicle mites, Demodex folliculorum and D. brevis (Acari: Demodicidae), in a selected human population in western New York, USA.
1986, Journal of Medical Entomology 23 (4): 384-388. PMID 3735343.
4. Zhao YE1, Guo N, Wu LP.
The effect of temperature on the viability of Demodex folliculorum and Demodex brevis.
Parasitol Res. 2009 Nov;105(6):1623-8. doi: 10.1007/s00436-009-1603-x. Epub 2009 Sep 23.
5. ZeynepTas Cengiz, Hatice Uce Ozkol, Yunus Emre Beyhan, Murat Ozturk, HasanYilmaz.
Evaluation of some chronical diseases in etiopathogenesis of demodicosis.
Dermatologica Sinica, Volume 35, Issue 4, December 2017, Pages 173-176.
6. D. Srikala, K. Satish Kumar.
Hypothyroidism associated systemic and peripheral disorders in dogs.
Animal Science Reporter, Volume 8, Issue 1, January 2014.
7. Greve JH, Gaafar SM.
Effect of hypothyroidism on canine demodicosis.
Am J Vet Res. 1964 Mar;25:520-2. PMID: 14125928.
8. de Almeida SF, de Sousa LB, Vieira LA, et al.
Clinic-cytologic study of conjunctivochalasis and its relation to thyroid autoimmune diseases: prospective cohort study.
Cornea. 2006 Aug;25(7):789-93.
9. Gilbert Smith, Alejandro Manzano Marin, Mariana Reyes-Prieto, Catia Sofia Ribeiro Antunes, Victoria Ashworth, Obed Nanjul Goselle, Abdulhalem Abdulsamad A. Jan, Andres Moya, Amparo Latorre, M. Alejandra Perotti, Henk R Braig.
Human follicular mites: Ectoparasites becoming symbionts.
Molecular Biology and Evolution, 21 June 2022. msac125, doi.org/10.1093/molbev/msac125.