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What
are the initiating factors for alopecia areata?
We do not know what activates and promotes the onset of alopecia
areata hair loss. There are several suggested factors that may influence
the course of alopecia areata.
- 1) Psychologic long term chronic stress
- 2) Shock and sudden extreme stress
- 3) Physical trauma
- 4) Local skin injury
- 5) Genetic predisposition
- 6) Viral/bacterial infection
- 7) Pregnancy/hormones
- 8) Allergies
- 9) Chemicals
- 10) Seasonal changes
1) Psychologic long term chronic stress. A wealth of case-lore
suggests that stress is an important precipitating factor in alopecia
areata. Various reports tentatively support the stress hypothesis
but so far it has only been shown by statistical correlation (Muller
1963, De Weert 1984, Perini 1984, De Waard Van der Spek 1989) -
no direct physical link has been demonstrated. Indeed, some investigators
refute stress being significant in alopecia areata (MacAlpine 1958).
One of the problems with defining the significance of some journal
reports on stress and alopecia areata is the lack control groups
for direct comparison and evaluation. Further, the subsequent stress
as a result of hair loss can confuse the issue in these inevitably
retrospective studies. Stress is suggested as an environmental trigger
in people predisposed to alopecia areata development (due to genetic
susceptibility for example) rather than the primary basis for alopecia
areata development (Muller 1963).
2) Shock and sudden extreme stress. There have been a number
of reports on individual cases where clearly defined sudden stress
events have preceded alopecia areata development. The emotional
trauma of a family death or being involved in a car accident without
major injury have been suggested as triggers for alopecia areata
onset.
3) Physical trauma. There is a reasonable amount of case
history evidence to show that physical trauma can trigger the onset
of alopecia areata. Anything that stimulates the immune system from
being hit on the head to an infection can be a potential trigger.
Only recently has there been a demonstration of a tangible link
between trauma and autoimmune diseases. Cells under physical stress
can produce heat shock proteins (HSPs). As the name suggests HSPs
are produced when cells are given heat shock. It has recently been
found that cells also produce these proteins after exposure to other
forms of stress such as inflammation, fever, irradiation, viral
infection, malignancy, oxidation, heavy metals etc. The HSPs play
a housekeeping role in immune system responses. These proteins have
been implicated in the autoimmune diseases rheumatoid arthritis,
lupus, and ankylosing spondylitis.
4) Local skin injury. Cuts, scrapes, and other abrasions
of normal haired skin are often the focus for the onset of a new
patch of hair loss in alopecia areata susceptible people. Ironically,
similar abrasions in areas of skin already affected by alopecia
areata can be the focus of temporary hair regrowth. Injury is known
to promote anagen hair follicle growth in skin immediately surrounding
the injured site.
5) Genetic predisposition. It has been shown that there
is a higher incidence of alopecia areata occurring in genetically
related individuals. This suggests that at least some people are
genetically predisposed towards the development of alopecia areata.
Several research groups have been examining the genetic make up
of people who develop alopecia areata and found some genes to be
much more common in people with alopecia areata compared to the
general population. It is generally believed that alopecia areata
susceptibility is polygenic - there are a number of genes which,
if present, make that individual more likely to develop alopecia
areata. The triggers for the actual onset of alopecia areata are
most likely environmental but susceptibility to development of alopecia
areata, the resistance of the alopecia areata lesion to treatment,
and its persistence and regression and its extent over the body
might be influenced by the presence and interaction of several genes.
6) Viral/bacterial infection. Cytomegalovirus infection
of hair follicles has been implicated by at least one research group
in development of alopecia areata (Skinner 1995). However, research
by other groups has failed to confirm the potential link (Garcia-Hernandez
1998, Tosti 1996). HIV infection has also been suggested as a potential
trigger for alopecia areata onset (Piras 1997, Grossman 1996, Cho
1995, Stewart 1993). Other dermatologists suggest general viral/bacterial
infections may promote the immune system into an inappropriate response
against hair follicles in susceptible people.
7) Pregnancy/hormones. The apparent link between hormonal
fluctuations and alopecia areata has been recognized for some time
(Sabouraud 1896, Sabouraud 1913). Most notable are the cases of
alopecia onset during late stage pregnancy. Women who already have
alopecia areata can find that they have complete, but temporary,
hair regrowth around the time of childbirth (Walker 1950). Puberty
and menopause have also been suggested as a time of potential alopecia
areata onset or remission.
8) Allergies. Statistical analysis shows that Caucasians
with alopecia areata and some form of atopy (Asthma, eczema, rhinitis)
are inclined to have hair loss that is more extensive and/or of
prolonged duration (Muller 1963, De Waard Van der Spek 1989). Interestingly,
statistical analysis of Indians with alopecia areata showed no such
link (Sharma 1996). This may suggest that the different genetic
composition of different races must be taken into account when explaining
susceptibility to alopecia areata development.
9) Chemicals. One "outbreak" of alopecia areata in workers
at a water treatment plant in a paper factory was linked to long
term exposure to the chemical acrylamide (Roselino 1996). Formaldehyde
and pesticides have also been suggested, although not proven, as
a potential influence in the development of alopecia areata. Isolated
case reports have suggested a link between alopecia areata development
and Zidovudine treatment of HIV (Geletko 1996), and Fluvoxamine
anti-depressive treatment (Parameshwar 1996).
10) Seasonal changes. A significant number of people with
alopecia areata find the extent of the hair loss cycles in time
with the seasons. Some people find the hair loss is much more extensive
in winter and have temporary, partial regrowth in summer.
Whatever the initiation factor it need not be permanent - rather
a short sharp shock may be just enough to tip the balance of the
immune system into autoimmunity. Once an autoimmune disease is initiated
it can be self perpetuating. Tissue destroyed in the early stages
of the disease can be broken down and the antigens presented to
immune system cells in the lymph nodes. This recruits more self
reactive cells which destroy more tissue producing more antigens
and so the cycle continues.
What
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