Dandruff is generally caused by fungi living on the scalp. The fungi eat up your skin and make it dry. The dry skin flakes off.
Dandruff shampoos work by killing the fungi. There are three main types of anti-fungals, zinc pyrithione is used in Head and Shoulders, selenium disulfide in Selson Blue. There is a third one not commonly used called ketoconazole that you may want to try.
There is also coal tar shampoo, which is not an anti-fungal, instead it slows skin cell growth and sloughs off the dead skin.
Selson Blue works well for me, I use it daily. If I go off of it for a few days the dandruff kicks into high gear.
The thing about dandruff shampoos is you have to use them with a certain regularity because even if you kill the fungi, the condition takes a few days to clear up, the damage to your scalp is done. You need to create a hostile environment for the microorganisms, and that takes time.
Your dandruff is probably caused by only one type of organism that thrives in particular climates. Next time you're there, you might get ahold of two or three shampoos and try them for a week each and see if it clears up. Then you know which is 'your' anti-fungal.
Not merely an insightful repository of analysis and explanations around the more profound aspects of our world, John Ralston Saul's exquisite Doubter's Companion includes some answers - acerbic accusations bundled free - to the more pedestrian issues:
"DANDRUFF: The ANSWER is usually vinegar. To some problems there are solutions.
"What we call dandruff is often the result of a PH imbalance on the skin, which shampoo exacerbates. Wash your hair with a simple non-detergent shampoo, soap, olive oil, beer, almost anything. Rinse. Then close your eyes and pour on some vinegar. The extremely cheap but natural sort—apple cider, for example—is probably best. The smell will stimulate interesting conversations in changing-room showers and your explanation will win you friends. Wait thirty to sixty seconds. Rinse it off. The smell will go away. So will your dandruff.
"All dermatologists, pharmacists and pharmaceutical companies know this simple secret. They don’t tell you because they make money by converting dandruff into a complex medical and social problem. By most professional standards this would amount to legally defined incompetence or misrepresentation.
"Dandruff shampoos that promise to keep your shoulders and even your head clean are harsh detergents and may promote baldness, which ought to constitute malpractice."
Actually, I think I'm mostly annoyed by your use of three pejoratives to try to make one point, and the fact you spelled pseudo wrong just irritates some other part of my brain. :)
Sure, dandruff and 'dry skin flakes' are separate things entirely.
Dandruff is generally regarded to be caused by the fungus Malassezia. This fungus does not enjoy an acidic environment.
(Healthy) human skin tends towards pH 4-5 (there seems to be some debate). Malassezia likes 5-8 (again, some debate). Reducing the pH / increasing the acidity would appear to have some non-psuedo, non-alternative-medicine, non-falsehood foundation.
Wikipedia says one cause of dandruff is yeast-like fungus. Perhaps PH plays a role in that. Also vinegar has cleansing properties and may be less drying than detergent, and dry skin is another cause of dandruff.
The word "vinegar" is notably absent from that link. That solely shows that harsh soaps are harsh (which as you may have noticed is axiomatic), not that vinegar isn't.
When I typed the word "may" I meant it. If it's medically established that properly diluted vinegar dries the skin I'd be interested in knowing that. Otherwise, it seems like reasonable speculation to me rather than pseudo-scientific BS.
I suffer from dandruff, tried a bunch of shampoos but they didn't work well. I saw this tip about vinegar, which I tried a single day then I gave up thinking this could be popular saying. I'll try again and report.
When you say 'this could be popular saying' are you meaning that it may be wrong because it's popular?
I'd be curious to know your results, in any case. I've had mixed outcomes from conventional (commercial shampoos) and have also been trying to identify causal factors (worse in winter, especially after a few days of wearing a beanie, worse when I'm staying near a high-pollution area, etc). It's all anecdata, but OTOH not beyond our abilities to thoughtfully analyse.
This unconscious bias went unnoticed to me (as expected, per definition). Thanks for pointing it :)
So far, my experiments with other shampoos where conducted a bit ad hoc. They're all anecdata. When I try with vinegar, I should try to rule out other causal factors first. I probably haven't done that in my first try. Otherwise, we can never be sure.
To be honest, I only went to see a single dermatologist, but my experience was bad. The dermatologist kinda overlooked and shrugged. I received a shampoo recommendation, but the dermatologist didn't say we should monitor the treatment or anything. From what I saw, she would keep recommending shampoos and I would try until I found one that worked. so I decided to try by myself.
Not my wisest moment. I should probably have seen another dermatologist.
Great book and great advice. Must be about 20 years since I tried this approach. Count me as a data point strongly supporting the use of vinegar to deal with dandruff.
"You use Head & Shoulders? But you don't have dandruff!" "Exactly!"