Alopecia is the medical term for hair loss. It covers any loss of hair from areas where it normally grows, whether that’s a small patch on your scalp, thinning across the top of your head, or hair falling out across your entire body. Alopecia isn’t a single condition. It’s an umbrella term for many different types of hair loss, each with its own cause, pattern, and outlook.
The Main Types of Alopecia
Hair loss can look very different from person to person, and the type you have determines whether your hair can grow back and what treatments might help.
Androgenetic alopecia (pattern hair loss) is the most common form of hair loss in both men and women. In men, it typically shows up as a receding hairline or thinning at the crown. In women, it appears as gradual thinning across the top of the scalp, usually without a receding hairline. This type runs in families and progresses slowly over years.
Alopecia areata looks different. It usually starts as smooth, round patches of hair loss on the scalp, sometimes appearing suddenly. In mild cases, hair often regrows on its own within a year. But it can also become more severe. Alopecia totalis means complete loss of all scalp hair, while alopecia universalis means losing hair across the entire body, including eyebrows, eyelashes, and body hair.
Traction alopecia results from prolonged or repeated tension on the hair, often from tight hairstyles like braids, ponytails, or extensions. Hair loss along the hairline is the most common pattern.
Scarring alopecias are a group of conditions where inflammation destroys the hair follicle itself, replacing it with scar tissue. Central centrifugal cicatricial alopecia most commonly affects women of African descent, starting as thinning at the crown that spreads outward. Frontal fibrosing alopecia causes the hairline to recede in a band-like pattern and can also affect the eyebrows.
Why Hair Falls Out
The underlying cause depends entirely on the type. Pattern hair loss is driven by hormones. A substance called DHT, derived from testosterone, causes hair follicles to gradually shrink. Over time, follicles that once produced thick, healthy hairs start making thinner, more fragile strands that fall out easily. Eventually the follicle produces hair so fine it’s barely visible.
Alopecia areata is an autoimmune condition. Your immune system mistakenly identifies hair follicles as a threat and attacks them. Immune cells cluster around the base of the hair follicle during its growth phase and release signals that disrupt the growth cycle, causing hair to fall out prematurely and preventing new growth. Antibodies against hair follicle cells are also found in people with this condition.
Other triggers include physical stress on the hair (traction alopecia), fungal infections like scalp ringworm, thyroid disorders, iron deficiency, medications like chemotherapy drugs, and inflammatory conditions that target follicles directly.
Scarring vs. Non-Scarring: Why It Matters
This is the most important distinction in hair loss. In non-scarring alopecia, the hair follicle stays intact even though hair falls out. Damage happens at the base of the follicle, leaving the stem cells and oil glands in the middle portion unharmed. That means hair can potentially regrow, either on its own or with treatment. Chemotherapy-related hair loss is a good example: the drugs kill cells inside the follicle so hair falls out, but the follicle itself survives, and hair typically grows back after treatment ends.
Scarring alopecia is permanent. Inflammation targets the middle of the follicle where stem cells live, destroying them and replacing the tissue with scar. Once that happens, the follicle openings in the skin close, and no new hair can grow from that spot. Early treatment to control inflammation can help preserve the follicles that haven’t been destroyed yet, which is why getting a diagnosis matters.
How Alopecia Is Diagnosed
A dermatologist typically starts with a physical exam, looking at the pattern of hair loss, checking for redness, inflammation, scarring, or sores on the scalp. Several simple tests can narrow down the cause.
In a pull test, the doctor grasps about 40 strands and gently tugs. If six or more come out, that signals active hair loss. A tug test checks for brittleness by pulling a strand from both ends to see if it snaps in the middle. Some dermatologists use a microscopic camera device that magnifies the scalp up to 100 times, measuring the total number of hairs and the diameter of each strand to track thinning precisely.
Blood tests can identify contributing factors like iron deficiency, thyroid problems, or excess androgens. If a scarring alopecia is suspected, a small punch biopsy of the scalp (about the size of a pencil tip) can distinguish between different types. Skin scrapings may be taken if a fungal infection is a possibility.
Treatment Options and What to Expect
For pattern hair loss, the goal is slowing the process and, in some cases, partially reversing it. Over-the-counter topical treatments and prescription medications can help, though results vary and treatment is ongoing. Stopping treatment typically means hair loss resumes.
Alopecia areata has seen significant treatment advances in recent years. For mild, patchy cases, hair often regrows on its own within a year without any treatment. For severe cases, the FDA has approved a new class of oral medications (JAK inhibitors) specifically for alopecia areata. Three of these drugs received FDA approval between 2022 and 2024 for severe cases in adults, with one also approved for adolescents aged 12 and older. These medications work by blocking the immune signals that drive the attack on hair follicles.
Scarring alopecias can’t be reversed once follicles are destroyed, but treatment focuses on stopping the inflammation before more follicles are lost. The earlier you start, the more hair you can preserve. For traction alopecia, the solution is straightforward: reducing tension on the hair. If caught early, the follicles recover. If the pulling has gone on too long, the damage can become permanent.
Emotional Impact
Hair loss affects far more than appearance. Many people experience significant anxiety, loss of confidence, and social withdrawal, particularly when hair loss is sudden or extensive. This is true across all types of alopecia and affects people of all ages and genders. If you’re dealing with hair loss that’s bothering you, seeing a dermatologist is a practical first step. Identifying the type early gives you the most options, especially for conditions where follicle damage can become permanent.