There are many urban legends regarding hair loss and alopecia. Many of these are false and perpetuated by advertising for products which claim to solve the problem.
Wearing a hat can cause hair loss.
For the vast majority of the population, wearing a hat does not cause hair loss. The theory is that wearing a hat somehow cuts off oxygen to hair and causes it to fall out. This is false on two fronts. First, just wearing a cap does not cut off the oxygen to your scalp.
Second, the hair shaft which you see on your head is actually dead anyway so there is no need for it to get any amount of oxygen. The only truth to the myth comes from people who wear very tight hats or turbans. The tight hat can pull on the hair causing a traction alopecia at the site of contact of the hat to the head.
Washing hair frequently can cause it to fall out.
This is completely false. On average, 100 hairs per day fall out of the body. Though you may see more hairs in the drain when you shampoo, this is only because you are removing the hair which already fell out. The actual act of washing hair does not cause it to fall out any more than it would normally, it just means that you see it in the drain instead of on your bed.
Hair loss comes from your mother’s side of the family.
In fact, the genetics of hair loss has not been completely worked out but at least one hair loss gene is actually autosomal dominant which means that it can come from either side of the family. Hair loss can skip a generation and may not occur to the same degree in relatives. For instance, even though your father is completely bald and you are starting to thin, this does not mean that you are destined to be completely bald.
Stress causes hair loss.
While this is true, the type of stress is not what most people consider stress. Deadlines at work and making sure you make all of your children’s activities cause stress, but not the type that will cause hair loss. When the body is physically stressed as in pregnancy, prolonged hospitalization, or surgeries, hair loss can occur. Fortunately, once the stress has resolved, the hair will start growing again.
Cutting your hair will make it grow back thicker.
This is unfortunately not true. Cutting hair short will make it appear thinner where longer hair will give the appearance of a greater density. This change may seem to cause a thickening of the hair as it grows but if you take photographs before you cut it and after you let it grow back to the same length, there will not be a difference.