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.1 Each hair follicle goes through this growth phase before taking a break and becoming inactive for a short while.
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. Many factors can upset this balance and stop your hair from growing normally. Let’s take a closer look at some of these.
Like 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.
Alopecia 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.
Aging 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.
Physical 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.
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.
Sudden 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.
Many medicines including birth control pills, calcium channel blockers, retinoids, beta-blockers, certain nonsteroidal anti-inflammatory drug (NSAIDs), certain antidepressants etc. can hamper hair growth and result in hair loss. If you find that your hair is thinning out after starting a new medicine, speak to your doctor to figure out if the medication could be causing it.
Thyroid 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.
Wearing cornrows, braids, hair extensions, and even tight ponytails can pull your hair and cause it to break off. Long-term use of these hairstyles can even damage hair follicles and lead to permanent hair loss. Harsh chemicals and extreme heat can also damage hair and cause it to break off before it grows to its full length.
Fungal infections of the scalp can cause hair to break off at the surface of the scalp and result in patchy hair loss. You may also have itchy, swollen, and reddened areas on the scalp if you have a fungal infection. This can be treated with antifungal medication.
Nutritional deficiencies can also hamper hair growth. And research indicates that iron deficiency can be one such factor which leads to hair loss. If you have an iron deficiency, you may also experience symptoms such as brittle nails, cracks at the corners of the mouth, fatigue, shortness of breath, and cold hands and feet. A deficiency of zinc, biotin, or protein may also lead to hair loss too. These deficiencies are usually seen in people who are on restrictive diets or have some medical problems which lead to malabsorption of nutrients.