At some point, most of us are going to experience hair loss.
In the United States, roughly half of all men (and women, too) will start showing signs of baldness by their 40th birthday, according to the Cleveland Clinic.
Even though modern folklore, and even some limited scientific studies, have suggested that the mother's side of the family is largely responsible for a genetic predisposition toward baldness, the truth is balding is not all our mothers' fault.
In fact, doctors now say baldness patterns are inherited from a combination of many genes on both sides of the family. There are some environmental factors that come into play, too.
Scientists are starting to inch closer to finding a cure for the missing hair problem. But so far there are only a few proven ways to prevent baldness and help grow back lost hair.
Hair loss, also called alopecia, is most often hereditary - passed down from generation to generation. But it can also be caused by environmental factors like poisoning, radiation, certain drugs, infections, hormone disorders, or nutrition deficiencies.
Also, physical stressors like sudden weight loss or pregnancy, or other physical or emotional shocks, can lead to temporary hair loss.
Hair loss can be completely normal
The most common kind of hair loss is male pattern baldness (androgenetic alopecia). Doctors estimate this condition may affect up to 80 percent of white men by their 70th birthday.
This form of hair loss can also be associated with other medical conditions like coronary heart disease and prostate problems for men, as well as hormonal imbalances in women, according to the National Institutes of Health.
It affects more than half of all women, too, and is caused by the sex steroid hormone dihydrotestosterone. Often in men, it'll start at the temples or in the back of the head, at the top.
In women, it can show up first near the front of the head, or in a widening of the scalp line, where hair becomes thinner.
Other types of hair loss can be a result of scarring damage from hot combs, weaves, chemical relaxers, and hair dryers, so it's important to be gentle with your hair.
Hair loss won't usually feel like much when it's happening. But sometimes it can be a warning sign of a larger health issue, especially if there's scarring on the scalp.
It's actually a normal thing for hair to fall out. Hair starts its life with a long growing phase, and usually about 80 percent of our hair is in this phase at any given time. But other hairs are getting ready to leave our heads.
The other 20 percent of our hair is going through a transitional period, and then a resting phase, where it falls out. We normally shed about 50 to 100 hairs a day this way. But after a fresh shampoo, that number can jump to around 250. That's okay, because we typically have have about 100,000 hairs on our heads at any given time.
The process of phasing out old hair typically takes around 3 to 5 months. Normally, at the end, a new hair starts growing from the empty follicle; but with alopecia, that doesn't happen.
The hair loss can be focal, and concentrated in one spot, or diffuse, and all over the head. Sometimes there's scarring, because the hair follicle is being destroyed, and this may be a sign there's a disorder present that should be investigated.
Even the best treatments have side effects
There are only a few proven ways that we know can treat baldness, but scientists are still searching for new cures.
One of the first successful treatments was invented by Guinter Kahn. It's called minoxidil, but you may know it better by its brand name: Rogaine.
It's usually applied to the scalp with foam or a dropper, twice a day. It helps re-grow hair and prevent new hair loss, too. Rogaine makes the hair-growing phase last longer, and enlarges and matures thin hairs. But it doesn't work for everyone.
"Usually only 30 to 40 percent of patients experience significant hair growth," the Merck Manual says.