- Causes of Patchy Hair Loss in Alopecia Areata? - Dr.Hanish Babu, MD
Alopecia areata is a localized, patchy, non-scarring type of hair loss, characterized by formation of one or multiple round or oval hairless patches. In contrast to patchy hair loss due to other causes like fungal infections, in alopecia areata, the skin in the bald area is smooth and normal. In some affected individuals, alopecia areata tend to recur at regular intervals.
Alopecia areata usually affects the scalp and beard areas, but other hair bearing areas can also be affected. Total loss of scalp hair is known as alopecia totalis and alopecia universalis denotes total loss of body hair, including the eyebrows and eyelashes.
Alopecia areata has a yearly incidence of 0.2% and various studies reveal that 1.7% of the population is afflicted by this mysterious recurrent, localized and patchy loss of hair. It usually appears in the first 3 decades of life, though no age is exempt. Both sexes are affected equally by alopecia areata.
What is the Cause of Alopecia Areata?
In addition to alopecia areata, there are many causes for hair loss that is patchy and non-scarring, like fungal infections, secondary syphilis, trichotillomania and pseudopelade.
Alopecia areata, or localized, patchy hair loss, is now known as a chronic, organ specific autoimmune disease affecting the hair follicles and, at times, the nails. The body’s immune system produces auto-antibodies against the hair follicles. These auto-antibodies, which mistakenly attack the body’s own cells, produce an inflammatory reaction around the hair bulb in the dermal layer of the skin. The interesting thing to note is that this inflammatory reaction does not produce any noticeable changes on the surface of the skin except the patchy hair loss. The autoantibody reaction is specifically directed at growing hairs which contain the black melanin pigment within the hair roots. The so-called overnight graying of hairs following an intense stressful incidence is due to this selective action of the attacking T cells against black hairs – only black hairs fall off and the white hairs are unaffected.
Alopecia areata is at times associated with other autoimmune diseases, like Hashimoto’s thyroiditis, autoimmune polyendocrinopathy and vitiligo.
Why Does the Body Attack its Own Hair Cells in Alopecia Areata?
Why the body’s immune system attacks its own cells is not yet clear, but there are various hypotheses regarding the underlying mechanism of autoimmunity in alopecia areata.
The predisposition to alopecia areata maybe genetically determined, which means it may run in families. Indeed, 10–20% of the patients with alopecia areata give a family history of the disease. The incidence may still be higher; it is possible that mild cases may go unnoticed and unreported in many instances. There are several reports of alopecia areata occurring at the same time in twins.
Alopecia areata is common amongst those afflicted with Down’s syndrome.
What are the triggering factors or risk factors that cause this localized, patchy hair loss in apparently healthy individuals?
Alopecia Areata: The Triggers
A variety of environmental factors may, individually or jointly, trigger the autoimmune response in alopecia areata. These environmental triggers include stress, infections, trauma, direct pressure, and, possibly radio frequency and electromagnetic waves produced by prolonged use of mobile phones. These are all based on observations of clinicians; no solid proof exists about the causative role of these environmental factors in alopecia areata.
- Stress: Intensely stressful periods preceding the appearance of the patchy hair loss is reported by an impressive number of patients with alopecia areata. The underlying mechanism may be altered immune response and neurological effects on the hair follicle triggering the inflammatory response against the hair roots. Quite a number of case reports cite examples of acute psychological trauma, higher number of stressful events in the preceding 6 months and a higher prevalence of diagnosed psychiatric disorders among patients with alopecia areata. It is important to note that stress may cause alopecia areata only in the genetically predisposed and not in all individuals.
- Infections: Like many other autoimmune disorders, alopecia areata has also been purported to be triggered by some hidden infections. Outbreak of a large number of cases within a close circle of friends and relatives provide credence to this infective theory. It is possible that, in predisposed individuals, certain bacterial or viral infections trigger the autoimmune response against the hair follicles.
- Dental infections: Alopecia areata of dental origin has been reported for more than one century. Because of similarity in the embryonic and structural origins of the tooth and hair, auto-antibodies formed against damaged tooth germ cells may attack the hair roots as well, a case of mistaken identity. This hypothesis is further bolstered by the fact that a part of the body similar in structure and development to hair and teeth, the nails, is also affected in some cases of alopecia areata.
- Trauma: Injury to the skin and damage to the hair follicles has been proposed as another reason for formation of auto-antibodies against the hair follicles in susceptible individuals.
- Direct pressure: Persistent direct pressure on the hair follicles from inappropriate postures and tight fitting helmets has also produced alopecia areata in some individuals.
- Mobile phones: Constant use of mobile phones without any ‘hands free’ devices can produce inflammatory reaction within the skin and cause damage to the hair follicles with resultant formation of the auto-antibodies. Recently many reports are also popping up in the media regarding the adverse effects of the electromagnetic waves of the mobile phones on other organs like the brain and the inner ear.
- Other triggers: Hormonal changes during pregnancy, certain toxic substances like the pesticides, anti-HIV and anti-psychotic medications and the presence of atopy or allergic diathesis have also been implicated as triggering factors in alopecia areata by various researchers.
To sum up, alopecia areata is an autoimmune skin disease induced by a variety of environmental factors in genetically predisposed individuals. Understanding these basic mechanisms will be helpful in effectively getting rid of and preventing the recurrence of this patchy hair loss.
Further Reading
- Is it Necessary to Treat all Cases of Alopecia Areata Hair Loss?
- What are the Causes of Reversible Patchy Hair Loss?
- Causes of Irreversible, Scarring Type of Patchy Loss of Hair
- Treatment of Alopecia areata: National Alopecia Areata Foundation
Sources
- Ralf P, Elis AO, Andrew GM. Hair Growth Disorders, in Fitzpatrick’s Dermatology in General Medicine. 7th Ed, 1: 753-777, 2008
- Messenger AG. Alopecia areata, in Rook’s Text Book of Dermatology, 8th Ed, 4: 66.31-66.38, 2010
- Shabnam M, Jerry S. Alopecia areata update. J Am Acad Dermatol. 2000; 42:549-66.
Disclaimer
The information given in this article is for educational purpose only so that patients are aware of the options available. No diagnosis should be made or treatment undertaken without first consulting your doctor. If you do so, the author or suite101 will not be responsible for any consequences. The images provided are for illustration purpose only.
Hanish Babu - Dr.Hanish Babu, MD is a dermatologist and a feature writer on Suite101.com with more than 200 articles related to skin diseases on the ...
