Hair Restoration Blog

Demodex folliculorum is a widespread skin parasite.  Demodex folliculorum is a microscopic creature in the form of an elongated and jointed worm.  Demodex folliculorum could be found on the skin surface, particularly on those parts of the skin with large sebaceous glands and on individuals affected with acne or seborrhea oleosa.

Demodex feeds on the oil and skin sebum so the more sebum the greater the number of Demodex folliculorum. While it is sometimes found on the surface of the skin, it is more commonly encountered in the substance of hair follicle comedo plugs, where five to twenty worms may be discovered in a single follicle. A similar species which is considered to be a variety of that discovered upon the skin of man infests dogs, mice and other mammals. However, none of these related demodex species are known to be transmissible to humans.

Demodex folliculorum infection is very common and around 80% of the adult population, both men and women, have a Demodex folliculorum infection. It is believed that the frequency of Demodex folliculorum is less in children.

There have been sporadic claims made about Demodex folliculorum and hair loss for over many years. Quite recently a theory has been put forward that patterned baldness could be associated with infection of hair follicles by the Demodex folliculorum parasite. By infiltrating the sebaceous gland of hair follicles the parasite causes an immune response and inflammation of surrounding tissue - so it is claimed. Through long term invasion, the parasite “exhausts” the hair bulb and shifts the hair cycle from anagen to telogen so more hair follicles stay in resting phase rather than growth phase.  That means less hair is seen on the scalp at any given time.  This theory is promoted by certain companies that just happen to have a range of products that destroy Demodex folliculorum. At least one of the companies has conducted research that allegedly showed 88% of 240 men (more than its rate in normal population) with male patterned baldness had Demodex folliculorum infection in their hair follicles. However, there are several problems with this theory:

1. Eighty percent of the normal population has Demodex folliculorum whether they have hair loss or not. The company conducting the research conveniently forgot to study normal haired people to find the frequency of Demodex folliculorum in people with a full head of hair.
2. Research has shown that there are frequently excessive numbers of the Demodex folliculorum parasite in eyelash follicles. However, people with pattern baldness do not lose their eyelash hairs.
3. There is a clear bias towards men having pattern baldness hair loss even though women are equally susceptible to Demodex folliculorum infection and at least some children are also infected. If Demodex folliculorum infection was causing inflammation that pushed hair follicles into telogen then one would expect to see some children with pattern baldness and women would be equally affected with hair loss. Indeed, women have a stronger immune system and so one might expect more women than men to have pattern baldness, but this is not the case.
4. If Demodex folliculorum was a key cause of pattern baldness it would be impossible for hair follicle transplants to work. Given thousands of transplant procedures are done every year and 80% of men have Demodex folliculorum infection, then most of the men with hair transplants must also have a Demodex folliculorum infection. In a hair transplant, follicles are moved from the back of the head to the top of the same individual. If the individual is infected with Demodex folliculorum one would expect that the transplanted follicles would either already be infected, or become infected in their new location. However, transplanted follicles grow in every individual who has had the procedure done and pattern baldness does not redevelop.
5. there is a widely available treatment to Demodex folliculorum infection called pilocarpine gel. However, using this gel on the skin does not promote any hair growth.

A theory for Demodex folliculorum infection in people with pattern baldness is that the sebaceous glands of alopecia affected hair follicles become larger and more active, producing oils at a faster rate, under the influence of dihydrotestosterone (DHT). The oils combine with dead cells from the hair follicle to make sebum. The sebum is a rich source of nutrients and this is the food that Demodex folliculorum eats. The oily food supply increases in most hair follicles affected by pattern baldness so these hair follicles can accommodate a greater number of Demodex folliculorum parasites. Rather than the parasites causing pattern alopecia. The parasite infection could be simply a consequence of pattern baldness rather than a cause of the hair loss.