Vitamin D and Hair Loss: Does Low Vitamin D cause Hair Loss?

Vitamin D is a popular topic of discussion.   Each and every day, we learn more and more about the potential benefits of vitamin D.  For example, vitamin D seems to help protect against developing certain types of cancers and it may even reduce the risk of developing neurological problems such as multiple sclerosis. The list of potential benefits of vitamin D is quite long, and a few are shown in the accompanying diagram.  The vitamin D story is an important topic, especially since so many of us are deficient in vitamin D.

But what role, if any, does vitamin D have in hair functions? Do individuals with low blood levels of vitamin D have hair loss?

There is no definitive research to suggest that low vitamin D causes hair loss. We simply don’t know if it does or does not. Furthermore, we don’t really know if low levels of vitamin D might have a negative impact on hair growth.  Certainly, there is accumulating evidence that vitamin D has some importance for normal hair function.

To understand how vitamin D works, it’s important to understand a few things. First, in order for vitamin D to do its job inside our cells, it usually needs to attach to the so called “vitamin D receptor”.  Once vitamin D binds to the vitamin D receptor a series of changes happen deep within our cells.

We know that severe abnormalities in vitamin D can certainly be associated with hair loss. For example, children born with a condition known as type IIa vitamin D dependent rickets inherit a defect in the vitamin D receptor.  These children have normal hair in the first few months after birth but then slowly lose hair around 3 months of age.  Many of these children have complete loss of all their hair.  This provides us with some information that vitamin D is important for hair growth.

There is additional scientific evidence that vitamin D has importance in hair growth.  Nowadays we can create a mouse in the laboratory that lacks the vitamin D receptor.  These mice are born with hair but then lose it after birth and are completely bald by age 8 months.

To date, there are only a few studies evaluating the role of vitamin D in human hair loss.  Some studies have shown that vitamin D when applied topically to the scalp can reduce the chance of cancer patients developing hair loss after being given certain types of chemotherapy.   However, this was found to be true only for some types of chemotherapy and vitamin D could not prevent hair loss following receipt of other types of chemotherapy.

We don’t really understand all the functions of vitamin D as it relates to hair growth and hair loss.  Furthermore, we don’t really know if low vitamin D has any association with hair loss. However, vitamin D is probably pretty important when it comes to overall hair health.  So until we learn more about vitamin D by doing more research, it probably makes sense that patients with hair loss strive for normal levels of vitamin D.

 

Can I receive donor hair for a hair transplant from another person?

Modern medicine has given us the miraculous ability to transplant hearts, lungs, kidneys, livers, pancreas, intestines, corneas and other organs from one person into another person. So, can we transplant hairs from one person to another person too?   It’s a great question and one that I'm asked at least once each week.   In theory the answer is yes, but in reality the answer is no.  Let me explain.

Suppose we have two people, let’s call them Rob and Greg. Rob wants a hair transplant but doesn't have enough donor hair to complete the procedure. Greg has plenty of hair and has offered to donate some of it. If Rob were to receive hair from Greg, and those hairs were transplanted into Rob’s scalp, they would be quickly lost or ‘rejected’. The reason is that Rob’s immune system would view Greg’s hairs as foreign invaders and quickly destroy them.  As a result, Rob would lose the hairs that were transplanted.

The reason that patients don’t reject organs such as lungs, hearts or kidneys when they are transplanted is due to the use of “anti-rejection drugs.” These drugs have many potential side effects and carry potential long term risks.  They can not be prescribed unless there is a significant medical reason for which an individual needs immunosuppression.  It is for this reason that a hair transplant is not performed from one person to another.

Interestingly, there are a few rare situations where it would be possible to receive donor hair from another person.  The first situation would be a hair transplant in identical twins.  Suppose I omitted to tell you that Rob and Greg are actually identical twins.  In that case, Rob and Greg have the same genetic material and a hair transplant could be performed without the need for anti-rejection drugs.  

The second situation would be if a bone marrow transplant were performed.  A bone marrow transplant is a medical procedure which is typically performed only if an individual is very ill, such as in an individual with cancer.  During a bone marrow procedure an individual undergoes a procedure whereby their own blood system and immune system is replaced by the immune system of another person.  So, if Rob received a bone marrow transplant from Greg, could Rob then receive hairs from Greg to perform a hair transplant? The answer is yes.  In fact, the Italian researchers Rosati and Bergamo studied this phenomenon and reported it to the public in their 1999 publication in the journal Dermatologic Surgery.  They studied the growth of hairs in a single patient who underwent a bone marrow transplant. The transplanted hairs grew extremely well. Bone marrow transplantation is a very complex procedure and carries several potential risks to the patient so this procedure can only be performed in those who are seriously ill. It can not be used in healthy individuals.

In general, it is not possible to perform a hair transplant using donor hair from another person.

Source: Rosati P and Bergamo A. Allogenic hair transplant in a bone marrow transplant recipient. Dermatol Surg 1999; 25: 664-5.

Drugs and Hair Loss: Is it Common?

Many patients with hair loss tell me that they think one of the medications they take caused their hair loss. How can I tell if this is the case?      

First off, sometimes it’s not possible to tell at all. Sometimes it’s only possible to give an “estimate” of how likely it is that a medication caused hair loss.  If a patient started a medication in January and notices hair loss in March or April of the same year, that increases the likelihood that that medication caused hair loss. However, there are dozens of other reasons why the patient may be losing hair and these have to be carefully explored.

Furthermore, some medications are more likely to cause hair loss than others.  These include blood pressure medications such as beta blockers or ACE-inhibitors, psychiatric medications such as lithium, SSRI antidepressants, allopurinol and vitamin A related medications.  Heparin blood thinners are also sometimes the cause of hair. These drugs typically cause a hair shedding condition known as "telogen effluvium." Cancer chemotherapy drugs also cause hair loss, and often this is a specific type of more profound hair loss called "anagen effluvium." There are over 500 medications that can cause hair loss, but these examples are some of the most likely.

Overall, hair loss due to a medication is not very common.  More times than not, another explanation for a patient’s hair loss can be found.

What's New in the World of Hair Research? Minoxidil.

5 % Minoxidil Foam vs. 2 % Minoxidil Solution

Minoxidil 2 % topical solution is approved for the treatment of androgenetic alopecia in women.   It is typically used twice daily. Although Minoxidil 5 % is formally approved for use only in men, it may also be recommended for women in some situations. 

Researchers from Germany and the United States set out to compare if once daily use of 5 % topical minoxidil foam formulation was just as good as twice daily 2 % minoxidil solution.

To test this, 113 women with androgenetic alopecia randomonly assigned to receive wither 5 % minoxidil foam (once daily) or 2 % minoxidil solution (twice daily) over a period of 24 weeks.

After 24 weeks of the study, researchers showed that once daily 5 % minoxidil foam was just as good as twice daily 2 % minoxidil solution.  Both formulations were able to increase hair counts and hair thickness in a similar proportion of women.  Women in the study actually preferred the 5 % foam over the solution reported that the foam was less likely to interfere with hair styling and less like to cause itch and dandruff. 

Reference:  Blume-Peytavi et al. A randomized, single-blind trial of 5% minoxidil foam  once daily versus 2% minoxidil solution twice daily in the treatment of androgenetic alopecia in women. J Am Acad Dermatol 2011.

Nails: The Final Stop En Route to a Complete Hair Examination

When I examine a patient’s hair, I generally examine the nails too.  Hair and nails are closely related in terms of their constituents and rely on similar nutrients for growth. In fact, I often tell my patients that hair and nails are like “cousins” and a lot can be learned by looking at the nails. 

For example, patients with the autoimmune hair loss condition alopecia areata may have changes in the nails, with the most common change being nail “pitting” or little dents in the nails. Patients with a rare scarring hair loss condition known as lichen planopilaris may also have lichen planus of the nails. Patients with hair loss from severe iron deficiency may have spoon shaped nails – a phenomenon known as koilonychia. The list goes on and on and these are three examples.

A close inspection of the nails can often reveal incredibly useful information about an individual’s hair and the cause of their hair loss.  The opportunity should not be missed.

 

How many hairs come out of each pore?

The hair follicles in our scalps are grouped together in bunches of 1 to 5 hairs.  These groups of hairs are called “follicular units.” This might come as a surprise to those who assume that each hair follicle opening contains just a single hair.  In fact, less than 20 % contain a single hair. Most follicular units contain 2 or 3 hairs; a small proportion contain 4-5 hairs.

In the picture on the right, 15 hairs can be seen emerging from a single follicle. Is this abnormal or normal? Why is this phenomenon occurring?

The phenomenon whereby multiple hair follicles emerge from a single follicle is called ‘tufting’ and these hair follicles are called compound hair follicles. This is may be a sign of a permanent scarring alopecia.  The photo on the right is from a patient with a rare scarring hair loss condition known as folliculitis decalvans.

Tufting occurs because the scarring process leads to permanent destruction of hair follicles as well as the surrounding tissue. This destruction causes many follicular units to merge together. The end result is that multiple follicular units end up sharing the same follicular opening.

 

Would I be a Candidate for a Hair Transplant ?

What type of hair loss conditions will a hair transplant be helpful and which will a hair transplant simply notwork?

For men and women who have hair loss due to androgenetic alopecia, a hair transplant is often a good option to improve hair density.  A hair transplant may be possible in those with hair loss following burns, traction alopecia, hair loss following radiation for brain cancer treatment, hair loss following some types of plastic surgery and hair loss in those with inactive scarring alopecias.

A hair transplant is not possible for those with hair loss due to alopecia areata, hair shedding problems (telogen effluvium and chronic telogen effluvium), and those with active scarring alopecias.

Diphencyprone (DPCP) for the Treatment of Alopecia Areata

Diphencyprone, or “DPCP” for short, A bottle of 1.5 % diphencyprone (DPCP)is a topical medicine used in the treatment of a specific autoimmune hair loss condition called alopecia areata.  It is typically used for those patients who have lost more than 50 % of their hair.  DPCP can be used to treat both adults and children with alopecia areata.

Patients with alopecia areata have DPCP applied to the scalp with a cotton swab once per week.  It typically causes a mild allergic reaction on the skin of the scalp with some itching during the 24 period after it is applied. It may cause the lymph glands of the neck to become slightly enlarged as well. Treatment is continued every week for at least 4-6 months to assess whether it is helpful or not.

DPCP can help regrow hair in 40 to 60 % patients with alopecia areata. The method by which it does this is extremely complex but at present, we think DPCP tricks the patient’s immune system. When DPCP is applied to the scalp the immune system is tricked into focusing its attention and resources on the DPCP chemical rather than attacking the hair follicle.

“Shock Loss” following Hair Transplantation

When hairs are moved from the back of the scalp into the front of the scalp, a proportion of the existing hairs in the front may sometimes be shed.  This phenomenon is called ‘shock loss.’  The hairs that were shed will regrow and shock loss a temporary phenomenon.  It is not fully understood why shock loss occurs, but it may be due to changes in blood supply.    Another mystery is why shock loss is more likely to occur in women than men.   I sometimes prescribe topical minoxdil before surgery and a few weeks after surgery to limit the likelihood of shock loss.

 

What's New in the World of Hair Research?

Flutamide for the Treatment for Androgenetic Alopecia in Women

Flutamide is an oral prescription drug which blocks androgen hormones and can sometimes be used in the treatment of women with androgenetic alopecia.  Italian researchers recently studied how well flutamide works in 101 women diagnosed with female pattern hair loss.   33 women were treated with flutamide and 68 women were treated with flutamide and a birth control pill. The researchers showed that both groups benefitted from treatment with flutamide.  The drug effectively blocked androgens and improved hair loss scores.  Benefits were seen after year 1 of treatment and extended into year 2.  They were maintained in year 3 and 4 of the study.

Conclusion: Flutamide is an oral drug which may be helpful in some women with female pattern hair loss.

Study source: Paradisi et al. Prospective cohort study on the effects and tolerability of flutamide in patients with female pattern hair loss. Ann Pharmacother 2011; 45: 469-75.

Iron and Healthy Hair

Iron has an important role in hair growth.  But consuming too much iron could potentially be harmful rather than helpful.  Patients often wonder if they should be consuming more iron to their help hair loss. Do you really need more iron?

Iron deficiency is the most common nutrition deficiency in North America. Iron deficiency refers to a state when the storage levels of iron in the body are reduced. When iron storage levels are reduced enough, the body can’t make enough haemoglobin and can’t make enough red blood cells to carry oxygen around the body.  When the haemoglobin levels drop below a certain level, a condition develops called "anemia."   Therefore, an individual may develop iron deficiency first and then develop anemia over time.

Iron deficiency is common and there are many causes. In fact, there are dozens of reasons to have low iron. It’s important to check with a physician to evaluate specific causes of iron deficiency.Iron deficiency is especially among pre-menopausal women on account of blood loss from menstrual cycles.    Because iron has an important role in hair growth, I routinely ask patients to get blood tests to measure haemoglobin levels as well as various iron tests.  The most common iron test is called the ‘ferritin test.’  For optimal hair health, I recommend patients take increase their daily intake of iron until ferritin levels rise above 40-50 ug/L. Levels below 20 ug/L can often be associated with hair shedding even if the patient has not yet developed an anemia.

If haemoglobin levels or ferritin levels are low, I recommend the patient be evaluated by a physician.  Sometimes an individual simply needs to consume more iron. This can come from meat, chicken, fish, grains and eggs as well as other foods.  Patients with significantly reduced iron levels, may also be advised by their doctor to take iron tablets.  

Hair Mathematics

We have about 5 million hairs on the human body and there are approximately 100, 000 hairs on the scalp.    Individuals with blonde hair have slightly more scalp hair follicles - about 110,000 to 120,000 and individuals with red hair have less – about 90, 000.  

It is currently believed that hairs on the scalp and body are all formed at birth and no new hair follicles are formed during our lives.  However, extremely exciting reserach over the last few years has shown that it is possible to stimulate the body to make new hair follicles under certain conditions, especially after wounding the skin.   This has been shown in mice, but we don't yet know how to apply this information to humans.   In the future, it may be possible to stimulate or trick the body to make new hair.

How Common is Hair Loss?

How Common is Hair Loss?

Hair loss is common. By the time we reach age 50, one out of every two people will have some form of hair loss. About 50-60 % of men and 30 % of women and will develop androgenetic alopecia by this age.  This translates into about 50 million men and 30 million women in North America. Other hairs loss conditions are also present in the population.  Most people, especially women, will experience temporary hair shedding at some point in their lives.  Common causes included iron deficiency, thyroid problems, pregnancy, weight loss, illnesses and certain medications.  10-30 % of black women experience a permanent form of hair loss known as central centrifugal cicatricial alopecia.  It leads to hair loss in the middle of the scalp and is associated with the development of scars deep below the scalp.

Other reasons for hair loss

Other hair loss diseases are less common.  However, it's likely that you'll know someone with the following conditions at some point in your life.  About 2 % of the population have, or will develop an autoimmune disease called alopecia areata.  This condition is often associated with hair loss in circular patches but can rarely be associated with total scalp and body hair loss.  About 1 % of the population will develop hair loss at some point in their lives from trichotillomania.  This is a form of hair pulling and plucking that may be associated with underlying emotional issues, including depression, anxiety or obsessive compulsive disorder.  There are dozens of other forms of hair loss too, but they are less common.

 

Hair Transplantation in Scars

Hair loss can sometimes be associated with scarring.  For example, some patients I see have hair loss from previous cosmetic surgery, including facelifts. Some patients have scarring from previous burns or trauma to the scalp.  In addition, there is an entire group of hair diseases known as “scarring alopecias.”  Can a hair transplant be performed into scars? Will the transplant be successful?

One of miraculous aspects of hair transplantation is that hair follicles can grow in scar tissue.  For patients with scars from cosmetic surgery, I will restore hair density in a single session.  For those patients with scar tissue from scalp disease, or other complex scarring processes, I will wait 2 years after the disease has been declared quiet or "burnt out."  At this point, I will generally recommend placing a few test grafts in to an area and observing the survival of these grafts over a 6 month period.  If the graft survival rate is high, I will proceed with surgery.  If the graft survival is poor, I will either declare the patient not to be a candidate for surgery, or place the patient on additional treatment to ensure the disease has truly become burnt out.

"Hair Cloning": Who? What? When? Where? and How?

Patients often ask me what new hair loss treatments are around the corner.  This frequently leads us into discussions about the technique of "hair cloning."  What is hair cloning? When will it be available to the public?

Hair cloning is presently an experimental technique used to markedly increase the number of hair follicles. At present, it is being developed, and is not available as a treatment.

The picture above shows the basics of hair cloning. To envision the process, I tell patients to imagine two visits to the hair clinic. In the first visit, which might only last 30-40 minutes, the patient would have 10-50 hairs removed from the scalp. These hairs would be taken away to a laboratory where special cells in the hair follicle (called dermal papilla cells) would be extracted from the hair follicles. These cells would then be multiplied in the laboratory to become millions of cells over the next 1-2 months. At the end of the second month, the patient would be invited back to the hair clinic for a second visit where these cultured cells would be injected into the scalp using a very small needle. New hair follicles would then be generated from these cells over the next 6-9 months. 

The concept of hair cloning is tremendously exciting. Patients with advanced hair loss could potentially have the entire scalp restored with these two visits. In addition, the technique could be modified slightly to treat many hair diseases besides androgenetic alopecia.

It’s not known exactly when the technique of hair cloning will be ready to the public. Several companies are working on the technique right now, and clinical trials are underway. There have been several challenges in perfecting the technique. For example, one challenge has been ensuring cultured cells retain their ability to produce a hair follicle once they are removed from the scalp.  When these dermal papilla cells are grown in the laboratory they sometime have a tendency to become 'tired' or 'lazy' and no longer want to produce a new hair follicle. Additional challenges include making sure that hair follicles emerge from the scalp at a precise angle and direction so that the hair cloning procedure looks natural.  One can imagine that if hair follicles emerge from the scalp in a haphazard way, with some pointing left and some pointing right, or some pointing forward and some pointing back, the outcome could look strange.

I tell my patients that the technique is still many years away, but will be revolutionize the way hair loss is treated when the technique is finally perfected.

Miniaturization: The Clue to the Early Diagnosis of Androgenetic Alopecia

One of the most common causes of hair thinning is androgenetic alopecia.  Men with androgenetic alopecia may notice hair loss at the top of the scalp as well progressive receding in the temples. Women with androgenetic alopecia notice thinning in the middle of the scalp.  The central hair part may become wider over time.  As hair thinning occurs the scalp becomes progressively more visible.   

I treat androgenetic alopecia with either 1) topical medications such minoxidil, 2) oral hormone blocking medications or 3) with hair transplantation. For some patients, I may recommend all three treatments. I encourage patients to consider using medical treatments in the early stages in order help maintain or improve the present hair density and prevent further loss over time.

Patients considering treatment for the very early stages of androgenetic alopecia often ask how I can absolutely sure they have androgenetic alopecia. Some of the doctors I teach ask the same question. How do you tell androgenetic alopecia is present if the patient does not actually have hair loss yet?What are the clues to the early diagnosis of androgenetic alopecia?

Androgenetic alopecia can be diagnosed based on the pattern of hair loss and by observing a process known as hair follicle “miniaturization.” When I lecture about androgenetic alopecia, I refer to miniaturization as the process by which hair follicles get skinnier over time.   It takes time for doctors to learn to identify hair follicle miniaturization, but I teach the following analogy to help others master this skill. 

Pretend that hair follicles are like tree trunks in the forest.  This analogy is kept in mind as the scalp is examined. If the size of the tree trunks is all the same – the patient does not have androgenetic alopecia.  If some of the tree trunks are fat and some of the tree trunks are skinny, the phenomenon of miniaturization is being observed. This is shown in the picture above. The most likely cause, by far, is androgenetic alopecia.

There are rarely other conditions that can be associated with miniaturized hairs besides androgenetic alopecia.  But this analogy is extremely important.  Many patients with concerns about hair loss end up receiving a diagnosis of androgenetic alopecia.  If there is no miniaturization, the diagnosis is wrong, and there is another reason for hair loss.

The Inheritance of Androgenetic Alopecia: Father’s Father ... Mother’s Father ... or Father’s Mother?

Androgenetic alopecia is common in the general population. In fact, the condition is often called “common balding”.  Approximately 50-60 % of men and 30-40 % of women will develop androgenetic alopecia by the age of 50.  

When I meet with patients, I generally ask about the hair characteristics of his or her mother and father.  I try to get a sense of his or her parent’s hair density and the age at which the parents started losing hair.   Although men and women with androgenetic alopecia often have a family history of androgenetic alopecia, it’s not absolutely necessary for the diagnosis.   In fact, a family history is least likely to be found in women diagnosed with androgenetic alopecia.  This is because the inheritance of androgenetic alopecia is much more complicated in women than in men.

There are many myths when it comes to hair loss and patients are often surprised to hear me say that the chance to inherit hair loss comes from both sides of the family tree.  Upon hearing this I commonly hear patients reply:

I thought hair loss came from the mother’s father?

or ... I thought hair loss came from the father’s mother?

or ... I thought hair loss came from the father’s father?

The main message is that hair loss is inherited from both mother and father and their respective sides of the family tree.  It’s possible for children to have high hair densities in adulthood even if dad has androgenetic alopecia.  Furthermore, it’s possible (albeit uncommon) for children to have significant androgenetic alopecia when dad or mom have minimal hair loss in adulthood.

Am I allergic to my hair dye?

Many individuals ask if they could be allergic to their hair dye.   The answer is more likely to be “no” than “yes”, but it is possible to be allergic to hair dyes.    In North America, over 60 million consumers color their hair.  Allergic reactions to hair products are probably under reported so we don’t know the exact prevalance.  

There are four main types of hair dyes on the market: gradual, temporary, semi-permanent and permanent. The most popular types of hair dyes are the permanent dyes and the permanent dyes are the most likely types of hair coloring products to cause allergy. Individuals who are allergic to hair dyes sometimes develop a rash on the neck, forehead, eyelids, ears or even the hands.   The scalp may be red, crusted and oozing fluid.   Individuals with severe hair dye allergies may also feel unwell.

The main culprit in permanent dyes to cause allergic reactions is a chemical called para-phenylenediamine, or “PPD” for short. Other chemicals in hair dyes may also cause allergic reactions.  Specialized allergy testing called patch testing, can sometimes be used to confirm if an individual is allergic to their hair dye.

Improving Eyebrow Density: Hair Transplantation vs Topical Medicines

Eyebrow hair loss can be distressing for both men and women and an increasing number of patients are requesting appointments specifically for eyebrow hair loss. Why are eyebrows important and what can be done to improve their fullness?

The 250-500 eyebrow hairs have an important function. Eyebrows help frame the face and frame the eyes.  They draw attention to the eyes.  Talented make-up artists can even style the eyebrows to draw attention away from certain areas of the face. Subtle movements of the eyebrows can instantly reveal changes in emotion.

When I meet with patients with eyebrow hair loss, the most important aspect of the consultation is to reach the correct diagnosis.  In some situations, the diagnosis is easy. Over-zealous styling over many years can frequently lead to thinning of the eyebrows. In other situations, reaching the correct diagnosis of eyebrow hair loss requires a bit of detective work.  Many people are surprised to learn that there are over 30 causes of eyebrow hair loss. Reaching the correct diagnosis is especially important for those considering hair transplantation.   Individuals with certain autoimmune or medical conditions will not achieve improvement with hair transplantation.

Overall, treatment options to improve eyebrow density are improving.  For some individuals, hair transplantation is a great option and the procedure can be performed in 2-3 hours.  For others, treatments with topical medications such as minoxidil, bimatoprost (also called Latisse®) or corticosteroids can help improve eyebrow hair density.

Telogen Phase: Exit Strategies for Hair

When I teach doctors about hair loss, I often begin by telling them that hair loss from the scalp is a normal phenomenon.  From the time a hair follicle first surfaces above the scalp, it is programmed to eventually be lost or "shed" from the scalp.  All hair follicles come programmed with an exit strategy. In fact, hair follicles have a meticulously regulated mechanism for every aspect of their growth.

All hair follicles proceed through four phases as they grow.  These phases are called anagen phase, catagen phase, telogen phase and exogen phase.  Hairs on the scalp spend about 2-6 years in the anagen phase, 3-5 weeks in catagen phase and 3 months in telogen phase.  At the end of telogen phase, hair follicles are shed in the exogen phase.  As these follicles fall out of the scalp and a new hair follicle pushes up from below.  All hair follicles come programmed with an exit strategy. It’s called exogen. This is why hair loss is a normal phenomenon.

If you reach up an grab a strand of hair on your scalp, it's likely in the anagen phase. In fact, 90 % of hairs on the scalp are in anagen phase. Less than 1 % of hairs are in catagen phase. 10 % are in telogen phase. 

Every day about 100 hairs on the scalp find themselves in the exogen phase and are shed from the scalp.  This is an important statistic to remember: the normal rate of daily shedding is about 100 hairs.   Loss of more than 100 hairs per day is abnormal and indicates excessive shedding.  A comprehensive evaluation will usually reveal the cause of a patient's excess shedding.