Banded or Ringed Hair
Q: I have a very rare genetic hair type and I was wondering if you knew anything about it as no one seems to have ever heard of it! My Great Grandmother, Grandmother, Mother and sister all have it too (and presumably it goes further back than that). It is 'speckled' or 'banded' hair. Essentially each hair follicle is 'banded' or spotted in slight ridges down the length of the hair.
When you look at my hair, you can see tiny little white spots on each hair from the root to the tip, evenly spaced. While the women of my family all have different coloured hair, we all have quite fine and straight hair in shades of ash (from blonde to dark brown). Hairdressers seem to find the speckling fascinating but I have yet to meet anyone outside my family who has heard of this, or seen it, and I would appreciate knowing more about it.
The trait is common in many breeds of mammals, notably among certain rodents and husky breeds of dog. In these animals the trait is often referenced by the term "agouti" which is from the rodent commonly found with the pattern of hair pigmentation.
When referenced as a disorder in human hair, the term Pili annulati is used. Pili Annulati is described as a disorder that results in ringed or banded hair, alternating bright and dark bands in the hair shaft. The dark bands are a manifestation of abnormal air spaces in the cortex of the hair. There is little to be found on this condition as it is quite rare, particularly among humans.
Apart from visual characteristics, it doesn't seem to create overly traumatic problems for hair care. Although the air spaces within the cortex could present a problem in long term coverage using hair color products.