Updated: Jul 9, 2020
Hair shedding is a natural part of the hair cycle. On average, people shed between 50-100 hairs every day, which does not make a significant difference in the hairs appearance because there is between 100-150 thousands hair follicles on an average scalp.
Since people are used to seeing a hair fall out here and there, it can sometimes be hard to determine if you are shedding more than normal. This can be problematic because increased shedding (along with several other early warning signs) can be an indicator of the onset of androgenic alopecia (pattern hair loss). If you are lucky, you may notice the increased shedding early, but if you are like most people, you will not realize it is happening until your hair starts to thin out.
Either way, you should talk to your doctor right away to determine the cause, and if it is pattern hair loss you will (likely) want to start treatment. More likely than not your doctor will recommend you use finasteride and minoxidil, two of the most effective FDA approved hair loss treatments available, but there’s a catch. Ironically, a common side effect of both treatments is a shedding phase, which can be a problem because people may perceive it as worsening the hair loss, when in fact it is doing the exact opposite.
I am writing this article to help you better understand the process of hair shedding and how it relates to minoxidil/finasteride so that you know what to expect when starting these treatments.
The hair life cycle
In order to understand shedding, you first need to familiarize yourself with the hair follicle growth cycle. Every single hair on your head is at a different point in the cycle, and can be categorized into one of the four stages:
Anagen (growth phase)
The anagen phase is the stage of the cycle when the hair is actively growing. It can last anywhere between 2-7 years and hair can grow up to 30 inches (about a half inch per month is average).
Catagen (transitional phase)
This is the phase where hair growth stops. The hair detaches itself from the blood/nutrient supply, but remains in the scalp. These hairs are called “club hair.” This phase usually lasts between 1-2 weeks before transitioning to the…
Telogen (resting phase)
This is the phase where the old hair is resting waiting to be replaced by a new anagen hair. The telogen phase lasts for around 3 months which is why 10-15% of hair is in this phase at all times.
Some articles make the claim that there is only 3 stages of the hair cycle, and that the hair falls out during the telogen phase, but this is not true. There is a fourth stage called the…
Exogen (shedding phase)
This phase is when the hair naturally falls out and gets replaced by the new anagen hair. Any hair that is lost naturally to shedding is transitioning from the exogen to the anagen phase.
What happens to the hair cycle when you go bald?
Although hair loss can occur from a number of factors such as stress, nutritional deficiencies and more, this article is going to focus solely on how androgenic alopecia affects the hair cycle.
The lengths of each phase that we described above are what is considered to be the baseline for a healthy growth cycle. It is when this cycle is altered and certain phases change lengths that hair loss begins to occur.
When dihydrotestosterone (DHT for short: the androgen responsible for pattern hair loss) interacts with hair follicles it will begin to slowly shorten the anagen phase. As the hair goes through its cycles, they will continue to be shortened. For example, a healthy hair follicle may have a growth cycle of 6 years, the next cycle would be 4, then 2, and so on. As the cycles are shortened, the hair will not grow as long or thick as it did in the previous cycle. This results in vellus (short, thin, unpigmented) hair replacing your once healthy hair, also called miniaturization.
The telogen phase may also be extended during hair miniaturization resulting in more hairs in it than normal, which results in a thinner appearance.
Now that you understand the hair growth cycle and how the balding process affects it, let’s talk about how both finasteride and minoxidil affect the hair cycle, and why it can cause shedding.
Finasteride works to block DHT and the damage that it causes to your hair follicles. A very common side effect that happens when you start taking it is, you guessed it, shedding. Fortunately, it usually happens within the first month of starting finasteride and normally lasts only a couple of weeks. It may sound counterintuitive but shedding is a sign that it is working, how you may ask?
When DHT levels are lowered it gives hair follicles a chance to “breathe.” By breathe I essentially mean that hair follicles that were in the prolonged telogen phase are (very quickly) pushed into the anagen phase. But, as a part of the process of the hair cycle the hair must first pass through the exogen phase. This causes many “club hairs” to be shed at the same time, but it is only to make way for new healthy hair.
Like I stated earlier, all of your hairs are normally in a different stage of the hair growth cycle. When you take finasteride, it synchronizes your hair follicles, which is why you may experience a drastic shed as all of the synchronized follicles fall out at the same time. But again, this shed is temporary and should only last a couple of weeks as your body adjusts to the lowered DHT levels.
Although the main mechanism behind pattern hair loss is DHT, low blood flow can affect the growth cycle too.
When your hair follicles are in the anagen stage, they are being fed a constant supply of oxygen and nutrients by the blood that they use to grow. If your hair is undergoing miniaturization from DHT, the shortened hairs require less and less blood. This is a vicious cycle because not only is your hair cycle being shortened by DHT, but the less blood there is, the slower growth will be.
Minoxidil is a vasodilator, meaning it works to widen blood vessels and increase blood flow. When blood flow is increased to miniaturized hairs, it can cause those hairs to prematurely enter the anagen phase. Just like how finasteride causes shedding, hairs that were in the telogen will be rapidly shed to make room for new anagen hairs to grow. Again, just like finasteride, this is a sign that the treatment is working.
Even though everyone’s hair cycle is slightly different there is one thing we all have in common: we all shed. Hair loss treatments can cause a drastic shed in the short term, but will leave you with more hair in the long term.
Hopefully now you understand how the hair cycle works and how hair loss treatments affect it so that you can remain optimistic throughout the shedding phase. Don’t give up, remind yourself of the long term benefits, stick through it and your hair will surely benefit.