Who wouldn’t want a gorgeous mane of long, thick hair? But sometimes it can seem like a herculean task to get your hair to grow out. Some among us also have to reckon with thinning hair or hair loss. If you’ve ever wondered why hair stops growing, we’ve got the goods on this perplexing phenomenon.
Normally, hair on the scalp doesn’t grow continuously. Each hair follicle goes through a growth phase known as the anagen phase during which it becomes longer and then goes into the telogen phase where it rests. Usually, a hair remains in the anagen phase for anywhere between 2–4 years and then in the telogen phase for around 2–4 months before it falls out. At any point in time, around 85–90% of the hair on a person’s head is in the anagen or the growing phase and the rest are in the telogen phase.
This cycle normally results in a person losing around 100 hairs in a day. Each hair follicle goes through this growth phase before taking a break and becoming inactive for a short while. The cycle then resumes again. But many factors can upset this balance and stop your hair from growing normally. Let’s take a closer look at some of these.
# GeneticsLike hair color, the length and thickness of your hair are also governed by your genes. In some people, hair naturally has a longer growth phase while in others it stops growing sooner. So if you’ve won the genetic lottery your hair may grow longer. For instance, Asians generally have a longer anagen or growth phase than Caucasians while Afro-Caribbeans have a growth rate that’s half of that of Caucasians.
# AgingAging changes your hair. Of course, we all know that it makes your hair lose pigment and become gray. But it can also slow down the rate of hair growth and cause hair strands to become smaller. Many hair follicles may also stop growing new hair with age.
# Alopecia AreataAlopecia areata is an autoimmune condition where your immune system mistakenly attacks cells in your hair follicles, resulting in hair falling out in patches. In some cases, hair may even completely fall out (alopecia totalis). Genetics is thought to play a part in the development of this condition. It has also been found that people with hay fever, vitiligo, Down syndrome, pernicious anemia, thyroid disease, and asthma have a higher risk of getting alopecia areata. In over 90% of cases, the hair grows back and bald spots disappear on their own within 12 months. Medication or phototherapy may also be recommended by doctors to treat this condition.
# Hereditary Pattern Baldness
Hereditary pattern baldness is considered to be the most common reason for hair loss. It’s caused by a combination of the aging process, hormone levels, and genetics. In people with this condition, the normal hair growth cycle is altered due to the influence of the male hormone testosterone, resulting in thinner and shorter hair. In time, hair growth may stop completely in some parts of the scalp. In men, this results in the typical pattern of thinning hair at the top or a receding frontline while in women hair loss may be more diffused.
# Physical Or Psychological StressPhysical or psychological shock can trigger a condition known as telogen effluvium. In people with this condition, more hair is prematurely pushed into the telogen phase. When this happens usually around 30% of your hair stops growing and moves into the resting phase (as opposed to the 10% in normal conditions). Severe psychological stress or other factors that stress your body such as surgery, significant physical trauma, extreme weight loss, severe infection, high fever, or illness can trigger telogen effluvium. The condition typically does not last longer than 6 months.
# Hormonal ChangesSudden hormonal changes such as is seen during pregnancy and menopause can also trigger telogen effluvium. But hair loss associated with these events typically resolves in 6–24 months. Hormonal fluctuations associated with polycystic ovarian syndrome can also lead to hair loss.
# Thyroid ProblemsThyroid problems can also cause your hair to thin out. Your thyroid gland produces the hormone thyroid which regulates many activities, including your metabolism. Both insufficient thyroid hormones (hypothyroidism) and excessive thyroid hormones (hyperthyroidism) can affect hair growth and result in hair loss. You may also notice other symptoms associated with thyroid disease if it’s at the root of your hair loss. Hyperthyroidism can cause weight loss, irregular heartbeats, anxiety, increased sweating, diarrhea, and muscle weakness, while hypothyroidism can result in sluggishness, constipation, feeling cold, less sweating, weight gain, a hoarse voice, and a puffy face.