Human heads are full of bacteria, but interactions between two dominant microorganisms can predict whether or not the unwitting host person has a bad case of dandruff.
The findings, published in the journal Scientific Reports, put the focus on the bacteria Propionibacterium and Staphylococcus, and take the blame off of fungi, which previously had been thought to be a primary driver of dandruff.
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"Dandruff is a common scalp disorder that has occurred for centuries and has a prevalence of nearly 50 percent in the worldwide population," lead author Zhijue Xu of China's Shanghai Jiao Tong University and his team wrote in the paper. They added that other scientists have studied the unpleasant, unsightly and often uncomfortably itchy problem for decades.
Dandruff primarily consists of flakes of dry skin mixed with sebum, an oily substance produced by glands in the scalp's skin. The condition is rare before puberty, peaks in the teens and early twenties, and declines with age thereafter. While special shampoos and lifestyle changes can help to control the formation of dandruff, there is no true cure for the condition.
To better understand this very common yet still mysterious disorder, Xu and his team investigated 174 dandruff samples collected from 59 Chinese people aged between 18 and 60 years old. These volunteers were recruited from the Shanghai Dermatology Hospital in China, and had varying levels of dandruff.
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Participants were asked to wash their hair 48 hours in advance of tests, and dandruff samples were collected from eight different sections of the scalp.
The scientists found that Propionibacterium and Staphylococcus essentially hate each other, with each inhibiting the presence of the other. Both are dominant forms of bacteria amongst hundreds of other types on the human scalp.
When dandruff was present, levels of Propionibacterium in the scalp region had decreased and levels of Staphylococcus had increased. Staph is frequently also found in the nose, respiratory tract and on other skin areas, but problems associated with it are well known to medical researchers. When the bacterium gets out of balance, it can cause everything from pimples to sinus infections.
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Based on their determinations, the researchers suspect that sebum could act as a food source for Propionibacterium. Higher levels of water on the scalp, in turn, may provide a suitable environment for the growth of this bacterium.
Xu and his colleagues believe that adjusting the balance of bacteria on the scalp, particularly by enhancing Propionibacterium and suppressing Staphylococcus, could reduce dandruff.
Now the literally million-dollar-plus question is how to accomplish this goal. Considering that some 3.7 billion people have excessive dandruff and are potential customers of an effective treatment, it is likely that many research teams will be studying the common disorder more in the near future.
A side benefit to a possible cure could be to reduce pet allergies. These are often caused by pet dander, which is a sneeze-promoting combination of dandruff and hair or feathers.