Hair as a Barometer of Health

An issue I have always had is dryness of the scalp and graying of the hair-two things I would like to understand a bit more about.

MH has indicated that the hair is an escape route for toxic gases and can be considered a marker for one's health. Thus a thick head of natural colored hair I would assume means a healthy body-at least to some degree.

The question then arises. How can hair tone and color(as a visible index of health) be improved? A couple of things that come to mind in assessing hair health are the causes of hair loss and two of them are thyroid function and the other is worms. Since we know that the hair drops out with the absence of a healthy thyroid and parasites then these would be avenues to look at when determining the cause of hair issues.

It seems that the thyroid would point to hormonal issues. Classical iridology states that the small intestine is the reflex organ for the thyroid. One of the culprits for burning off the small villi lining the SI is phytic acid found in wheat products. This impairs the SI and obstructs energy from reaching the thyroid. This is only one small piece of the puzzle.

My guess is that parasites rob the body of nutrients that would ordinarily be required for the production and maintainence of healthy vibrant hair.

My question for MH is what he feels are the main causes of unhealthy hair and how can we use the hair (and scalp) as a barometer of health. Also how can we mainatain a good healthy head of hair?

Thanks