Alopecia is a broad term for hair loss, and it comes in many forms. The first distinction doctors make is whether your hair loss is non-scarring (the follicles are intact and regrowth is possible) or scarring (the follicles are destroyed and hair loss is permanent). Within those two categories, there are several specific types, each with different causes, patterns, and outcomes.
Non-Scarring vs. Scarring Alopecia
This is the most important fork in the road when it comes to hair loss. In non-scarring alopecia, the hair follicle openings are still visible on the scalp, there’s no obvious inflammation, and the skin looks normal. The follicle is still alive, which means hair can potentially grow back. Most common types of hair loss fall into this category.
In scarring alopecia (also called cicatricial alopecia), the follicles are replaced by scar tissue. The scalp may look shiny or atrophic, and the follicle openings disappear entirely. Inflammation, sometimes visible and sometimes only detectable under a microscope, damages the follicle and the oil glands around it. Once a follicle is scarred over, it cannot produce hair again, which is why early identification matters so much.
Androgenetic Alopecia (Pattern Hair Loss)
This is by far the most common type of hair loss. It’s driven by a combination of genetics and hormones, specifically a hormone called DHT. High levels of DHT shrink hair follicles and shorten the hair growth cycle, so each new strand comes in thinner and finer until the follicle eventually stops producing visible hair altogether.
In men, this typically shows up as a receding hairline and thinning at the crown. In women, it tends to cause diffuse thinning across the top of the scalp while the hairline stays intact. It’s a non-scarring type, so the follicles are still technically there, but without treatment the miniaturization process is progressive.
Alopecia Areata
Alopecia areata is an autoimmune condition in which the immune system attacks hair follicles, causing hair to fall out in smooth, round patches. It affects about 2% of the global population, with a lifetime risk of roughly 1.7 to 2.1%. It’s more common in children and young adults and slightly more prevalent in women.
The condition exists on a spectrum. Some people get one or two small patches that regrow on their own. Others lose most or all of their scalp hair, a presentation sometimes called alopecia totalis, though definitions vary widely (some experts define it as 80% or more scalp hair loss, others as 100%). When hair loss extends beyond the scalp to eyebrows, eyelashes, and body hair, it’s sometimes called alopecia universalis. These are all considered the same underlying disease at different levels of severity.
Three FDA-approved treatments now target the immune pathway behind alopecia areata. These medications, called JAK inhibitors, work by blocking the signaling pathway that drives immune cells to attack hair follicles. In clinical trials, roughly 23 to 40% of patients achieved significant hair regrowth depending on the specific drug and dose. One is approved for adults only, one for ages 12 and up, and the most recently approved (in 2024) requires genetic testing before starting due to how some people metabolize it. Side effects are notable: upper respiratory infections occur in about 30% of patients, and the drugs carry warnings for serious infections, cardiovascular events, and blood clots.
Telogen Effluvium
Telogen effluvium is a reactive type of hair loss. Something shocks your system, and two to three months later, you notice hair falling out in handfuls. What happens is that a large number of hair follicles get pushed prematurely into the resting (telogen) phase, then shed all at once.
The list of triggers is long: high fever, childbirth, severe infections, major surgery, psychological stress, thyroid problems, stopping birth control pills, crash diets low in protein, and certain medications. The good news is that once the trigger is addressed, hair typically recovers without treatment within six to eight months. From the point you first notice the shedding, it usually resolves within three to six months. The hair doesn’t fall out in patches like alopecia areata. Instead, it thins diffusely across the entire scalp.
Anagen Effluvium
Anagen effluvium looks similar to telogen effluvium in that hair falls out rapidly and diffusely, but the mechanism is different. Instead of follicles being pushed into a resting phase, the fast-dividing cells at the base of the follicle are directly damaged while hair is still actively growing. The hair shaft becomes thin and brittle, then breaks off near the scalp.
The most common cause is chemotherapy, which targets rapidly dividing cells throughout the body. Hair matrix cells are some of the fastest-growing cells you have, which makes them especially vulnerable. In most cases, hair regrows after treatment ends, though there are reports of permanent hair loss when the stem cells in the follicle are destroyed.
Traction Alopecia
Traction alopecia is caused by prolonged physical pulling on the hair. Tight braids, cornrows, ponytails, buns, hair extensions, and dreadlocks are common culprits. It also affects people who wear tightly pinned caps, helmets for extended periods, or head coverings that pull on the hairline. Combining tight styles with chemical treatments like relaxers or straighteners increases the risk.
Early on, traction alopecia is reversible. You might notice small bumps around the follicles, tenderness, or thinning along the hairline or wherever the tension is greatest. If the pulling stops, hair grows back. But if the tension continues for months or years, the follicles scar over and the loss becomes permanent. If your hair hasn’t regrown after several months of leaving it alone, that’s a sign the damage may be irreversible. Traction alopecia is unusual in that it straddles the line between non-scarring and scarring. It starts as non-scarring but can progress to scarring if it’s not caught early.
Scarring Alopecia Types
Scarring alopecias are less common but more consequential because the hair loss is permanent. They’re classified by the type of inflammation involved.
Lichen planopilaris (LPP) is one of the most frequently diagnosed scarring alopecias. The immune system attacks the upper part of the hair follicle, causing redness, scaling, and eventually smooth, shiny patches of scarred skin. A related condition, frontal fibrosing alopecia, causes the hairline to slowly recede backward and can also affect the eyebrows. Both are more common in women.
Central centrifugal cicatricial alopecia (CCCA) starts at the crown and spreads outward in a circular pattern. It disproportionately affects Black women and may be linked to both genetic factors and styling practices, though the exact cause is still debated.
Folliculitis decalvans involves bacterial infection and inflammation around hair follicles, leading to pustules, crusting, and progressive scarring. A hallmark feature is “tufting,” where multiple hair shafts emerge from a single follicle opening as surrounding follicles are destroyed.
Discoid lupus erythematosus is a form of lupus that targets the skin, including the scalp. It causes thick, scaly plaques that scar and can permanently destroy follicles in the affected areas.
How These Types Are Diagnosed
Doctors use a combination of clinical examination, patient history, and specialized tools to tell these types apart. One key tool is trichoscopy, a magnified examination of the scalp and hair using a handheld or video dermoscopy device. It can reveal whether follicle openings are preserved (non-scarring) or destroyed (scarring), distinguish early pattern hair loss from telogen effluvium, and even help predict how alopecia areata will progress. Different conditions leave characteristic clues: yellow dots at follicle openings point toward alopecia areata or pattern hair loss, while irregular white patches suggest the scarring seen in lichen planopilaris. If you’re having a trichoscopy exam, you’ll typically be asked not to wash your hair for two to three days beforehand.
A scalp biopsy, where a small sample of skin is examined under a microscope, is sometimes needed to confirm a diagnosis, particularly for scarring alopecias where the type of inflammatory cell involved determines the specific condition and guides treatment. A simple pull test, where a doctor gently tugs on a group of hairs to see how many come loose, can help gauge whether active shedding is occurring and roughly how severe it is.