We all know that hair grows in cycles. Scalp hair is replaced every four to six months, while hair on the rest of your body grows about one inch a month.
But what does this cycle mean for your hair growth regimen? If you’re like most people, you probably think that you need to follow the same hair growth cycle as everyone else in order to have healthy, full locks. But this is not always the case. In fact, there are many factors that can affect your hair growth cycle and how you should take care of it.
This article will explore the basics of the hair growth cycle so that you can better understand why and when you should follow a particular regimen. Armed with this knowledge, you’ll be able to create a routine that works best for your individual hair type and growth cycle.
Table of Contents
The Hair Growth Cycle
The hair growth cycle is a series of steps that your scalp and hair follicles take to create new hair. The cycle starts with anagen, the phase in which your hair grows. Anagen lasts about two years, and during this time, your hair grows at a rate of about 1/2 inch per month.
Your hair then enters catagen, a phase in which the hair falls out and is replaced by a thicker intermediate layer. Catagen lasts about two weeks and is followed by telogen, the lengthiest phase of the cycle. Telogen can last anywhere from six to twelve months, but usually lasts around three months. Once telogen ends, your locks reach their final length and are called an end product.
The Hair Follicle
The hair growth cycle is a continuous process that starts before birth and continues until the old hair falls out. The growth phase begins when the follicle, or root, of the hair cell is activated. This happens as a result of an injury to the scalp, such as from a cut or a sunburn. The follicle produces new cells and hormones, which help it grow.
During the anagen phase, the follicle is active and growing. This lasts for about two years in normal circumstances. Then, in the catagen phase, the hair stops growing and becomes dormant. This lasts for about four weeks in normal circumstances. Finally, in the telogen phase, the hair falls out and new ones start to grow.
The Density of Hair
There are three phases in the hair growth cycle: Anagen, Catagen and Telogen. And while everyone’s hair growth is different, there are some general trends that can help you understand your hair’s cycling.
Anagen is the phase of hair growth where new hair grows. This phase lasts around two months and is characterized by a lot of new cell proliferation and growth. The thickness of your hair during this phase will be slightly higher than normal, but it will eventually settle back down to its regular thickness once the cycle finishes.
Catagen is the transitional phase between anagen and telogen. In this phase, your scalp temporarily shrinks due to decreased production of the hormone testosterone (which helps stimulate hair follicle growth). This period usually lasts around four days, but it can last up to a week in some cases. During catagen, your hair will become noticeably thinner and may even fall out. However, once telogen starts, all the lost hairs will grow back and the thinning process will be reversed.
Telogen is the resting phase where most of your existing hair falls out. It lasts for about three months on average, but it can last anywhere from two weeks to six months in some cases. During telogen, your scalp produces less testosterone which signals follicles to stop growing and enter into dormancy. Eventually, all of the lost hairs will grow back during anagen stages 2-4 (although perhaps at a slower rate).
The Layers of the Hair shaft
The hair shaft is made up of several layers. The outer layer is the epidermis, which is the protective outermost layer of the skin. Underneath the epidermis is the dermis, a thicker layer that contains blood vessels and other cells responsible for hair growth and maintenance. The dermis is separated from the cortex, or hair follicle, by a thin film of sebum and sweat.
The cortex is where all the hair growth happens. It’s lined with cells that produce keratin, a protein essential for hair formation and growth. Keratinocytes (the type of cell that produces keratin) are actively dividing and secreting new keratin when they reach their maximum capacity. Newhair cells then grow from these progenitor cells to replace those that have died.
From there, the shaft continues to grow downward as individual hairs emerge from the follicle and join together into bundles called microserial projections or MPs. These MP’s become progressively smaller as they move toward the scalp, until they disappear beneath the surface of the skin.
The Epidermis
Your hair growth cycle is a continuous process that starts with the onset of hair shedding, and eventually culminates in the new hair growth phase. The average human hair grows about one mm per month, which amounts to a total of 0.5-1 cm over the course of a year. However, your hair will continue to grow until it reaches its natural stopping point – around 75 cm for women and 80 cm for men.
There are several factors that affect your hair growth cycle, including your genetic makeup, lifestyle choices, and environmental factors. The following are five key stages in the hair growth cycle: initiation, anagen, catagen, telogen, and fall out.
Initiation
This is the initial stage of the hair growth cycle where you begin losing hair. Your scalp starts producing more sebum (a oil produced by the skin), which attracts dirt and oils from your scalp’s surface. This accumulation results in balding or thinning patches on your scalp due to excess sebum production.
Anagen
This is the longest stage of the hair growth cycle and accounts for 90% of all hairs that are grown each year. During this phase, your follicles (the cells that producehair) undergo a prolonged increase in cell division (33 times). This increased activity results in thicker and longer hairs that are typically darker because melanin (a pigment responsible for color) is synthesized at a higher rate during anagen.
Catagen
Catagen
The Dermis
The dermis is the layer of skin immediately beneath the epidermis. This thin layer of tissue helps protect the underlying muscle and nerve cells, and provides a foundation for the hair growth cycle.
During childhood, hair follicles proliferate and produce hair. As we age, this process slows down. The reason for this slowdown is still unknown, but it may have something to do with declining levels of hormones or decreased production of new cells in the scalp.
The dermis can still play an important role in hair growth by supporting new hair growth cells and encouraging them to divide. In addition, the dermis can help direct newly generated hair follicles towards the scalp where they will be most useful.
The Scalp
The hair growth cycle is a chronological process that takes place in the scalp.1 The cycle begins when the follicle, or mini-nucleus, on the skin’s surface starts to grow. This happens at the base of the hair shaft, which is where new hair grows. Follicles are about 2 mm in diameter and can grow up to 3 mm every month.2
After the follicle has grown for about two months, it starts producing an enzyme called kératinase, which helps to break down keratin.3 Keratin is a protein that makes up most of our hair shaft and protects the follicle from damage.4 This process is known as keratinization.5
Keratinization results in the formation of small plugs in the dermal papilla (DP). These plugs keep oil and sweat from getting into the scalp and blocking hair growth.6 The DP also contains melanin, which gives hair its color.7 Once keratinization is complete, Matrixyl 3000 (a peptide), dht (dihydrotestosterone), and other hormones start working together to stimulate hair growth.8
The length of time it takes for new hair to grow can vary depending on a lot of factors like genetics, age, sex, diet, stress levels and health conditions. However, on average it takes about 4-6 months for full growth to take place9