Glossary of Hair Loss Terms

When you first start experiencing hair loss and inevitably end up online searching for “Why Am I losing My Hair!?”, you’ll run into a lot of terms, some of which you’ve seen before and others you’ve never seen and can barely pronounce. Here’s a list of common terms that pertain to hair loss. This isn’t meant for diagnosis, but rather for information. If you are experiencing hair loss, please consult your physician or a dermatologist that specializes in hair loss.


Loss of hair as a result of illness, functional disorder, or hereditary disposition. The medical term for hair loss.

Alopecia Areata

A disease that causes sudden smooth, circular patches of hair loss (shedding). It is thought that it is caused by the body forming antibodies against some hair follicles. It can result from a number of reasons, such as stress and genetics.

Alopecia Totalis

A condition that results in no hair on the scalp, which begins as alopecia areata.

Alopecia Universalis

A condition that results in no hair on any part of the body including eyelashes, eyebrows, and scalp hair; develops from alopecia areata.


The growing phase of hair, usually lasting between two and six years.


General term referring to any male hormone. The major androgen is testosterone.

Androgenetic Alopecia

Hair loss resulting from a genetic predisposition to effects of dihydrotestosterone (DHT) on the hair follicles. Also termed female pattern baldness and male pattern baldness, hereditary alopecia, and common baldness.


A term used to describe the simple act of gluing a hairpiece onto the scalp.


Chemical treatment, usually of cancers, using drugs that have high levels of toxicity, frequently causing temporary alopecia.


The highest part of the head


The outer surface of hair, composed of overlapping scales made of colorless keratin protein. It gives hair luster and shine and also provides some of its strength.

Dihydrotestosterone (DHT)

Male hormone thought to be the main cause for the miniaturization of the hair follicle and for hair loss. DHT is formed when the male hormone testosterone interacts with the enzyme 5-alpha reductase.

Female Pattern Baldness

Progressive thinning of hair throughout the entire head caused by genes, age, and hormones. It usually develops at a much slower rate than male pattern baldness.


A saclike structure just below the surface of your scalp. It is the sheath within which hair grows.

Hair Shaft

Filament (hair) projecting from the epidermis that provides protection and warmth.

Hair Weaving

A process by which a hairpiece (synthetic or human hair) is attached to existing hair on scalp through braiding or another interweaving process.

Male Pattern Baldness

The most common type of hair loss; caused by hormones, genes, and age, it is usually progressive in nature. It affects the central and frontal area of the scalp and often results in a pronounced U-shape configuration.


Region toward the middle of the scalp.


The destructive process by which dihydrotestosterone (DHT) shrinks hair follicles; a key marker of androgenetic alopecia.

Nonscarring Alopecia

A broad category of different types of hair loss, including androgenetic alopecia. The hair follicle remains intact, thus increasing the likelihood that hair loss can be reversed.


An artificial replacement.

Scarring Alopecia

Patchy hair loss with obvious sign of scalp inflammation.

Senescent Alopecia

The type of hair loss that naturally occurs with age, when both the duration of hair growth and the diameter of the hair follicle decrease.


The resting phase of the hair cycle that usually lasts approximately three months.

Telogen Effluvium

The second most common form of hair loss (androgenetic alopecia is the first). A condition that causes an increased number of hairs to enter the telogen or resting phase. The additional shedding usually occurs in response to various stresses such as emotional trauma, post-pregnancy and illness, major surgery, and certain medications. Telogen effluvium can be delayed (occurring a few months after the stressful incident) or chronic (unresolved).

Telogen Loss

Loss of hair during resting phase of hair or “natural” loss.

Traction Alopecia

This refers to hair loss that occurs due to traction placed on hair. Traction alopecia is commonly seen with braids, pony tails, and other hairstyles that create pulling on the scalp.


A type of alopecia caused by the constant pulling and twirling of a specific area of scalp. The hair loss usually improves once the habit is stopped; however, in some severe cases it is permanent.


The crown area of the scalp.