Your hair is constantly going through phases of growth and loss. In fact, most people lose on average between 50 and 100 hairs every day, according to the American Academy of Dermatology. Unfortunately, in many people these phases of growth and loss become irregular, or even stop altogether, resulting in thinning or bald spots on the body. One area where this problem can become most apparent is on the sides of the head.
Pattern baldness is a common reason you may begin noticing thinning spots on the sides of your head. Commonly referred to as androgenetic alopecia, pattern baldness causes your hair cycles to shorten and new hairs to have more superficial roots, resulting in hair falling out easier. Pattern baldness is often hereditary, according to the Mayo Clinic.
Auto Immune Disease
Hair thinning may also be caused by alopecia areata, an autoimmune disease. With this disease, your body's immune system starts attacking your hair follicles, causing your hair to go through cycles of falling out and growing back, resulting in varying levels of hair loss, from thinning to bald spots or complete baldness. Alopecial areata is relatively common; the National Alopecia Areata Foundation estimates that 4.7 million people in the United States alone suffer from the disease.
Scarring can also affect hair growth on the sides of your head. Known as cicatricial alopecia, this hair loss cause occurs when the hair follicles are scarred by inflammation due to skin conditions including lichen planus and lupus. In this condition inflammation destroys the stem cells and sebaceous glands for the hairs on the scalp, resulting in thinning or bald spots.
Thin spots can occur on the side areas of your head after major shocks to the body, such as a car accident, disease or even an emotional hardship such as the death of a family member. This type of hair loss is known as telogen effluvium, and occurs when physical or emotional shock to the body forces hair prematurely into its resting phase, causing it to fall out more frequently.
Hair loss can also occur on the sides of the head through hairstyles that pull the hair tightly away from the scalp, placing stress on the hair follicles along the sides of your head. Known as traction alopecia, this type of hair loss occurs with hairstyles such as buns and ponytails.