Hereditary hair loss - The medical term is androgenic alopecia. Both men and women develop this type of hair loss, which is the most common cause of hair loss worldwide.
It means that you’ve inherited genes that cause your hair follicles (what each hair grows out of) to shrink and eventually stop growing hair. Shrinking can begin as early as your teens, but it usually starts later in life.
In women, the first noticeable sign of hereditary hair loss is usually overall thinning or a widening part. When a man has hereditary hair loss, the first sign is often a receding hairline or bald spot at the top of his head.

Age- With age, most people notice some hair loss because hair growth slows. At some point, hair follicles stop growing hair, which causes the hair on our scalp to thin. Hair also starts to lose its color. A woman’s hairline naturally starts to recede.

Alopecia Areata - Alopecia areata is a disease that develops when the body’s immune system attacks hair follicles (what holds the hair in place), causing hair loss. You can lose hair anywhere on your body, including your scalp, inside your nose, and in your ears. Some people lose their eyelashes or eyebrows.

Cancer treatment -If you receive chemotherapy or have radiation treatment to your head or neck, you may lose all (or most of) your hair within a few weeks of starting treatment.
Hair usually starts to regrow within months of finishing chemotherapy or radiation treatments to the head or neck. Dermatologists can offer medication to help hair grow back more quickly.

Childbirth, illness, or other stressors-A few months after giving birth, recovering from an illness, or having an operation, you may notice a lot more hairs in your brush or on your pillow. This can also happen after a stressful time in your life, such as a divorce or death of a loved one.

Telogen Effluvium - diffuse loss of hair which may occur 2 to 4 months following childbirth or from high fever, acute illness, physical and emotional stress and crash dieting.

Chronic Illness - eg. Too little biotin, iron, protein, or zinc If you’re not getting enough of one or more of these, you can have noticeable hair loss. Thyroid diseases, syphilis and connective tissue disease are examples which may cause hair loss.

Scalp Diseases -Fungal and bacterial infection, and other local scalp diseases. A scalp infection can lead to scaly and sometimes inflamed areas on your scalp. You may see what look like small black dots on your scalp. These are actually stubs of hair. Some people develop a bald spot.

Hair care - If you color, perm, or relax your hair, you could be damaging your hair. Over time, this damage can lead to hair loss.
If you often wear your hair tightly pulled back, the continual pulling can lead to permanent hair loss. The medical name for this condition is traction alopecia.

Hormonal imbalance -A common cause of this imbalance is polycystic ovary syndrome (PCOS). It leads to cysts on a woman’s ovaries, along with other signs and symptoms, which can include hair loss. Stopping some types of birth control pills can cause a temporary hormonal imbalance. Women who develop a hormonal imbalance can develop thinning hair (or hair loss) on their scalp.

Medication -A possible side effect of some medications is hair loss. If you think a medication is causing your hair loss, ask the doctor who prescribed it if hair loss is a possible side effect. It’s essential that you do not stop taking the medication before talking with your doctor. Abruptly stopping some medications can cause serious health problems.