Many people mistakenly believe dandruff is caused by dry
scalp, frequent shampooing or poor hygiene. These
popular misconceptions can lead to ineffective, and
sometimes inappropriate, treatments, and make it even
harder on those who have dandruff - half of adults with
dandruff are more self-conscious about their appearance.
Researchers now believe dandruff is a medical condition
caused by an overabundance of an organism that normally
exists on everyone's scalp - even people who don't have
the condition. This is important information for the
millions of Americans who feel self-conscious and
embarrassed about their appearance due to dandruff.
Dandruff typically begins to appear in puberty, and the
incidence is highest at age 40. Because people with
dandruff often do not seek medical attention, no one
knows exactly how widespread the problem is, but an
estimated 63 million Americans - or one in three adults
- have experienced dandruff symptoms.
million people suffer from seborrheic dermatitis, a more
severe form of dandruff that affects scalp and skin. In
fact, more people in the U.S. have dandruff problems
than arthritis (40 million) and smoking addiction (48
these millions needlessly suffer the flaking, itchiness,
redness and scalp inflammation caused by dandruff. Most
people do not realize that these symptoms, which range
from slight to severe discomfort, can be successfully
What causes dandruff?
is a minor infection of the scalp caused by an
overabundance of a micro-organism called Pityrosporum
ovale (P. ovale), a yeast-like fungus that is part
of the normal skin flora.
The notion that P. ovale might contribute to
dandruff was first proposed more than 100 years ago, but
only in the past 20 years has research been able to
substantiate this theory. Understanding that dandruff is
a medical condition is essential in selecting a
treatment that will return the scalp to its natural
Dandruff is a medical
- not cosmetic - condition
In the past, dandruff and
seborrheic dermatitis were seen as two different
conditions. Seborrheic dermatitis was treated with
corticosteroids and dandruff was viewed as more of a
cosmetic concern, and treated with shampoos and potions
supplied by the cosmetics industry.
Around the 1960s and '70s, dermatologists began to use a
number of new techniques to study skin structure and
functions, including the growth of epidermal cells,
which showed that epidermal cell turnover (the
production and shedding of the uppermost layer of the
skin) was increased in patients with dandruff. At that
time, dermatologists assumed that it was the increased
epidermal cell turnover, or "hyperproliferation,"
that was causing dandruff, and that P. ovale
colonization was secondary.
It is now evident that the opposite is true: P. ovale
overgrowth occurs first, and increased epidermal cell
turnover is secondary. Hyperproliferation occurs because
the skin is growing and flaking more rapidly as a result
of the yeast presence.
How does P. ovale
The research supporting
the idea that P. ovale is a primary culprit
emerged during the 1980s, and is based on the findings
present in both patients with seborrheic dermatitis
and dandruff, as well as normal subjects who have
with P. ovale causes the recurrence of
dandruff problems; and
- if the
condition is treated with drugs whose common
mechanism or mode of action is antipityrosporal, it
The rapid growth of P. ovale often is triggered
by an imbalance in environmental factors such as
climate, heredity, diet, hormones and stress. As the
body's natural defenses fight the excessive growth of
this organism, the results are the symptoms of dandruff
- flaking, scaling and itching.
Under normal conditions, P. ovale yeasts can live
on the skin without causing any problems. For example,
one study found that yeast-like organisms made up 46
percent of scalp flora in people without dandruff
problems; 74 percent in those who had dandruff, and 82
percent in those who were diagnosed with seborrheic
Other causes of
However, the presence of P.
ovale is not the sole factor contributing to
dandruff problems. When, for whatever reason, the body's
balance is disturbed, one of several immune responses
often are produced in dandruff patients.
For a long time, effective
therapy for dandruff and seborrheic dermatitis has been
seen with compounds whose only common link was
antipityrosporal activity. But proof of this
relationship was lacking until the introduction of
antifungal drugs - in particular, ketoconazole.
- One is
the production of antibodies, which are
immunoglobulin molecules that react with a specific
antigen (a substance capable of inducing a specific
immune response and reacting with the products of
Certain studies show the highest
titers of antibodies to P. ovale are found in
patients with the highest amounts of dandruff.
or an overreaction of the immune system to an
antigen, also probably contributes to dandruff.
Hypersensitivity reactions have the same mechanisms
as those of protective immunity, except that while
the latter protects against disease,
hypersensitivity leads to tissue damage and disease.
The environmental factors linked to dandruff may
contribute to hypersensitivity reactions in dandruff
there is substantial evidence that P. ovale
feed off the lipids and proteins present in the skin
and then secrete lipase or other enzymes.
increased P. ovale found in dandruff patients
may facilitate lipase activity, during which the
organisms digest skin lipids and turn them into
irritant fatty acids, causing skin inflammation and
tissue damage. This may lead to the skin reaction
associated with dandruff.
This lipase activity
indicates that in addition to hypersensitivity, the P.
ovale release toxic substances or chemicals that
may contribute to the development of a fungal
The role of ketoconazole in dandruff therapy The
mechanism of action of ketoconazole has been extensively
studied. Studies with various fungal species have shown
that ketoconazole acts primarily by damaging the fungal
cell wall, leading to its death.
many of antifungal drugs have produced a good inhibitory
effect on P. ovale, studies have shown that ketoconazole
was the most powerful.