Hair Growth Phases
The hair that grows all over our body moves through four stages of growth Anagen, catagen, telogen and early anagen/exogen
Anagen phase
the anagen phases is known as the ‘growing phase’ of the hair cycle, this is the longest phase and can last up to 3-5 years on some areas of the body. However certain areas including eyebrows, genitals and underarms move through this phase at a much faster rate. During the anagen stage the hair within the follicles are continuously growing until they reach the end of their lifespan, The hairs are connected to the hair matrix (base of the follicle) and the dermal papilla is imbedded within the base of the hair.
Catagen phase
also known as the transition phase of hair growth, this occurs at the end of the anagen stage and lasts for 10 days. During this time the growth of the hair slows down and starts to detach from the hair matrix.
Telogen phase
The telogen phase, otherwise known as the resting phases takes around 3 months to complete. The hair completely detaches from the matrix during this period as new hair is starting the form at the base. The hair usually remains in the follicle however some shedding can occur,
Exogen phase
The hairs will shed during this phase naturally or helped with washing, brushing or exfoliating. 50-100 hairs can shed from any one area during this phase of growth which can last for months. New hairs are forming within the follicle and will be entering the anagen phase where the cycle begins again
Factors that effect hair growth:
o Stress
Stress can cause havoc in the body including the loss of hair. Often people experiencing high and prolonged levels of stress will experience thinning or loss of hair on their scalp, face and body. Conditions such as alopecia can be trigged by stress conditions.
o Diet and lifestyle
Living a sedentary lifestyle and consuming an extremely poor diet whether it be unhealthy foods or limited foods can affect hair quality and hair growth over time. Hair can become oily, dry or brittle.
o Genetics
Genetic background directly influences the speed and density of hair growth.
o Hormones
Shifts in hormones causing imbalances often affect the speed and type of hair growth. For example during menopause many older women may experience an increase of vellus hair on the face but a decrease of terminal hair on the body, thinning of the brows usually occurs as well. During pregnancy many women notice an increase in the speed of their hair growth and thickness however on the scalp they notice shedding and thinning as a result of the hormonal changes.
o Hair removal- waxing and shaving
Different types of hair removal can have different effects on hair growth. Shaving often increases speed and thickness of growth where as waxing synchronises growth cycles and slowly thins the area.
o Thyroid condition
A common early sign of hypothyroidism (hashimotos syndrome) is shedding of the hair on the tails of the brows, usually the hair doesn’t grow back.
o Alopecia
Alopecia is a condition causing the hair follicles to no longer product hair. Usually triggered by immune disorders, stress or genetics. It can effect men or women and cause temporary or permanent hair loss
o Trichotillomania
An obsessive habit causing sufferers to pull out the hair on the brows and through the lash line causing long term damage to the follicles.
Hair anatomy
Hair is made of a protein called keratin and can be broken down into three layers:
Medulla– the innermost part of the hair, it is only apparent in large thick hairs and contains air and transparent cells
Cortex– the middle layer of the hair shaft, it contains keratin proteins, lipids and is mostly responsible for the colour of the hair. The cortex provides strength and texture to the hair fibre.
In addition;
- Disulfide bonds are found in the cortex layer of the hair shaft
- These bonds are the strong chemical links that hold together the proteins in your hair
- Disulfide bonds are what gives our hair its volume, curl and shape
- How strong and tight these bonds are will determine how curly our hair is
When chemically processing the hair these bonds are effectively ‘straightened’ to be able to temporarily redirect the hair growth pattern.
The cuticle– the outermost layer of the hair, it is made from flattened cells that overlap each other. Appearing like scales it is a thin and transparent layer that protects the cortex of the hair. This layer is one of the main layers of importance when concerning lamination, tinting and dying treatments.