Pathologies of the Hair

Often, if we think about our hair, it’s only to wish we had someone else’s! But for an individual with a hair disorder, returning to his original hair becomes the greatest desire. In this lesson, learn the medical terms used to describe hair pathologies.

Hair Types & Hair Follicle Life Cycle

You love your hair. You hate your hair. These are the two normal feelings most individuals feel. But beyond wrestling it into a trendy style, having highlights put in, or getting it routinely trimmed, most of us don’t truly think about our hair. But, for individuals experiencing a hair disorder, just having hair can become the dominant desire! Before we explore the various pathologies of hair, let’s review a few basic facts regarding these important strands.

First, there are two types of hair:

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  1. Vellus hair: the fine, soft hairs covering most of the body
  2. Terminal hair: the courser, larger hairs found on the scalp, and after puberty, on the chest, underarms, and groin as well

Secondly, despite its passive appearance, our hair is extremely active! Human hair follicles cycle through three different phases: growing, involuting, and resting. These phases are affected by inward hormonal changes and external factors, such as chemical or heat exposure.

It is normal for a person to lose between 25 to 100 hairs daily. So, when you finish your shower and notice a glob of hair over the drain, don’t panic! This is just part of the life cycle of the hair. However, for some individuals, this cycle is disrupted or altered, resulting in pathology of the hair.


The first set of hair disorders we will explore is broadly classified under the term alopecia. It is a very elegant sounding word, which means hair loss or baldness. When you hear the word ‘bald,’ you may immediately think of an elderly man with a shiny scalp, but in actuality, there are many types of baldness. The word alopecia stems from the Greek word for ‘fox.’ What does a fox have to do with baldness? Well, foxes are prone to mange, a disease in which patches of hair fall out!

Alopecia areata is an autoimmune condition in which an individual loses a distinct patch or patches of hair. Most often, the onset of this disorder is rapid, only taking a few days for bald areas to develop on the scalp (most commonly), chin, extremities, or in the eyebrows. For unknown reasons, the body turns against itself, attacking the hair follicles, causing them to shrink and stop growing regularly. The course of alopecia areata is extremely unpredictable; the bald patches can come and go spontaneously.

There are two specific subsets of alopecia areata:

  • Alopecia capitis totalis describes a patient who experiences total hair loss from the scalp
  • Alopecia universalis describes a patient who experiences total hair loss from all hair-bearing regions of the body

Most patients are asymptomatic other than the hair loss, but the emotional toll that this disorder causes cannot be underestimated. The use of corticosteroids, both injectable and topical, can be used to help slow the rate of hair loss in affected areas. However, there is no known cure for alopecia areata.


Another type of alopecia is androgenetic alopecia, more commonly known as male pattern baldness. Now is the time to think of an older man you know who has a shiny crown exposed. Got his image in your mind? Good, then you already have an idea of the end result of this condition. It begins with the front hairline receding, then an ‘M’ shaped pattern of the remaining hair develops, followed lastly by only a horseshoe of hair remaining on the sides and back.

Although it appears that the hair is falling out never to regrow, interestingly enough it’s not. At least, not really. In male pattern baldness, the terminal hair follicles shrink and begin producing vellus hairs. This condition is due to fluctuations in the male hormone, androgen, and genetics; hence the name androgenetic alopecia. There are several treatments available through the miracle of modern medicine. Some modalities are less invasive, such as Rogaine, others are more invasive, such as hair transplantation.

When females begin to experience this same type of hair loss, in which terminal hairs convert to vellus hairs, it is termed female pattern baldness. Unlike men, women tend to experience a widening of the central part and thinning on the crown and top of the scalp only. Again, the condition is due to androgen and genetics. Women are more likely to experience psychological consequences (i.e., being self-conscious), as baldness in women is not considered a ‘normal’ part of aging, as it is in men.


The next disorder we are going to examine deals with an excess of hair, so in sorts, the opposite of alopecia. Hirsutism is the development of excessive dark, course hair on a woman’s face, chest, or back. In essence, a woman begins to develop the hair growth pattern of a man.

Hirsutism to some degree can be genetic. Certain families and ethnicities are just more prone to growing darker, courser hair. However, significant hirsutism usually stems from a hormonal imbalance. Specific conditions, such as polycystic ovary disease or Cushing’s syndrome, cause an increase in the androgen hormone. This same hormone is responsible for secondary pubic changes seen in males and is the culprit for hirsutism in females.

Luckily, now there are many treatments available to help women with this condition, including oral contraceptives, creams, or laser therapies. In days gone by, these women had to live with the condition or make a living from the condition. Ever hear of a bearded lady? Well, she was probably suffering from hirsutism.


Lastly, folliculitis is an infection of the hair follicle. The infection may be caused by bacteria or a fungus, which infiltrates the hair follicle pore due to an injury to the hair follicle or the surrounding skin. Clothing that is too tight causing a friction rub, shaving with a dull razor, or acne can all cause damage to the hair follicle, allowing infection to take root.

Once the offending organism has taken up residence in the hair follicle, it often leads to redness, swelling, and usually the development of pustules in the affected area. Folliculitis is commonly classified as superficial or deep, depending on the depth of the infection. Superficial folliculitis is much easier to treat and resolves rapidly, without causing scarring or permanent hair loss that may occur with deeper infections.

Lesson Summary

In summary, hair is an extremely busy accessory to our bodies. It is constantly cycling through growing, involuting, and resting phases. Unfortunately, there are some disorders of the hair that can disrupt this cycle.

Individuals suffering from alopecia are experiencing hair loss. There are many types of hair loss, including the autoimmune disorder of alopecia areata. This condition results often in a clearly defined patch or patches of baldness. Furthermore, alopecia areata can present as total scalp baldness (alopecia capitis totalis), or total body baldness (alopecia universalis), as well.

More commonly is androgenetic alopecia, or male and female pattern baldness. Remember, male pattern baldness usually progresses from a receding hairline, to an ‘M’ pattern of remaining hair, to finally only a horseshoe of hair left around the sides and back of the scalp. Whereas, women with female pattern baldness tend to experience central part widening and/or thinning on the crown or frontal area of the scalp. Conversely, a female with excessive dark, course facial or chest hair is suffering from hirsutism.

Lastly, if the hair follicle pore becomes infected, it is termed folliculitis. This condition can be due to a bacterial or fungal infection but is always preceded by damage to the surrounding skin or pore itself first. This condition can be painful; however, it usually resolves quickly once the appropriate treatment is given.

So, the next time you are tempted to wish for someone else’s locks or declare that you’re having a ‘bad hair day,’ be grateful your hairs are healthy and where they should be!

Learning Outcomes

When you are finished, you should be able to:

  • Describe human hair and the human hair cycle
  • Identify and discuss the pathologies that affect human hair
  • Recall the treatment options available for the different hair pathologies

Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.


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