I have recently read several articles which I found fascinating and which explained to me the current scientific thoughts on dandruff. First remember that our scalp (and skin in general) is teeming with bacteria and fungi!! This is actually very natural and normal. An old estimate was 1 million of these little things per square centimentre! If you have dandruff the number went up a little bit to 1.2 million. (J. Soc. Cosmet. Chem., pgs 111-139, 1976). Therefore having the creepy crawlies is nothing to cause alarm.
Shampoo manufacturers in particular Procter and Gamble, have actually done a great job of find out what causes dandruff. Dandruff is now thought to be linked to three factors
1. Sebum - the natural oil produced by the skin and the fungus food!
2. A specific fungus - Malassezia globosa- which consumes certain oils found in sebum leading to production of an acid (oleic acid) that disrupts the cells of the scalp causing them to slough off
3. Individual susceptibility - meaning that not everyone will produce sebum in the quantity needed to get the fungus to multiply and not everyone's scalp will react the same way to the presence of oleic acid. Some will get dandruff others won't. 50% of people get dandruff and 50% don't.
The research was fascinating. Scientists have even gone the extra mile to decode the genome of this yeast (meaning find out the DNA sequence to see what kind of proteins it makes) in the hope of developing more effective ways to kill/control it.
So there you have it, the definitive answer to the cause of dandruff! (Sources : J Cosmet Sci, pg 81-2, 2006; J Investig Dermatol Symp Proc, pgs 15-9, 2007 and PNAS, vol. 104 no. 47 18730-18735 , 2007. ). I would add that many of the oils (including my beloved coconut oil) that naturals will use actually contain triglycerides and even oleic acid. If you are suffering from dandruff, cutting back on these oils may be useful.
I have received many questions about itchy scalp and dandruff. I sort of drew my own line in the sand because although these are hair related issues, they really do fall more into the medical field. I would really encourage anyone who has issues with dandruff to see a dermatologist especially if the dandruff is not resolved by using an over the counter specialist dandruff shampoo. These shampoos are very effective against dandruff so you may not have dandruff at all if they don't work. It could be eczema or another skin disorder or it could be severe dandruff - whichever way, see your doctor.
The picture is an unrelated image of E.Coli - nothing to do with the scalp, just symbolic and because I like their sausage shape!