Hair loss, also called alopecia, can cause gradual thinning, excessive shedding, breakage, or bald patches on the scalp or other hair-bearing areas. It may be temporary or progressive and can affect people of any age or gender. Because many types of hair loss look similar but require different approaches, an accurate diagnosis is the first step toward effective management and protecting healthy hair growth.
Types of Hair Loss
Every day, it is normal to lose roughly 50-100 hairs.
How does my hair grow?
There are 3 main phases of hair growth:
- Anagen – actively growing hair; most hair is in this stage (hair length depends on the duration of anagen)
- Catagen – in between phase that lasts 2-3 weeks where the hair growth stops and the follicle shrinks; ~ 1-3% of hair is in this stage
- Telogen – resting phase that lasts for 1-4 months; ~ 10% of hair is in this stage
Why am I losing my hair?
Hair loss occurs when the normal hair-growth cycle is disrupted, hair follicles become smaller or inflamed, hair shafts break, or follicles are permanently damaged. The cause may be hereditary, hormonal, autoimmune, nutritional, medical, medication-related, or connected to hair-care practices.
Common causes of hair loss include:
- Genetic and hormonal factors that cause androgenetic alopecia, also known as male-pattern or female-pattern hair loss
- Physical or emotional stress, high fever, serious illness, surgery, childbirth, rapid weight change, or crash dieting, which can trigger excessive shedding called telogen effluvium
- Autoimmune disease, including alopecia areata, in which the immune system attacks hair follicles and often causes smooth, round patches of hair loss
- Thyroid disease, polycystic ovary syndrome, and other hormonal or endocrine conditions
- Nutritional deficiencies or inadequate intake of iron, protein, vitamin D, zinc, folate, or vitamin B12
- Medications and medical treatments, including chemotherapy and certain medicines that interrupt the hair-growth cycle
- Tight hairstyles, extensions, chemical relaxers, bleaching, frequent heat styling, or repeated pulling that causes traction or breakage
- Fungal infections or inflammatory scalp conditions
- Scarring alopecias, in which inflammation damages and replaces hair follicles with scar tissue
- Compulsive hair pulling, known as trichotillomania
- Age-related changes in hair density and growth
More than one cause may be present at the same time. For example, hereditary pattern hair loss may occur alongside stress-related shedding or a nutritional deficiency.
What are the Symptoms of Hair Loss?
Hair loss does not look the same for everyone. Symptoms may develop suddenly or gradually and may affect the entire scalp, follow a recognizable pattern, or occur in isolated areas.
Signs and symptoms can include:
- Gradual thinning on the crown or top of the scalp
- A widening center part
- A receding hairline or thinning at the temples
- Increased shedding in the shower, on a pillow, or in a hairbrush
- Smooth, round, or oval bald patches
- Hair breakage or hairs of noticeably different lengths
- Loss of eyebrows, eyelashes, beard hair, or other body hair
- Short, tapered “exclamation point” hairs around a patch of hair loss
- Scalp itching, burning, tenderness, pain, redness, bumps, flaking, or scaling
- A smooth or shiny scalp with fewer visible follicle openings, which may indicate scarring
- Changes in the fingernails or toenails that occur with certain autoimmune forms of hair loss
Some types of alopecia cause no scalp discomfort or visible inflammation. Sudden, patchy, rapidly progressing, or painful hair loss should be evaluated promptly.
How Is Hair Loss Diagnosed?
Hair loss is diagnosed by identifying its pattern, timing, associated symptoms, and possible triggers. A dermatologist will review your medical history, medications, diet, recent illnesses or stressful events, hormonal changes, family history, and hair-care practices. The scalp and hair shafts are then examined for thinning, shedding, breakage, inflammation, scaling, scarring, and loss of follicle openings.
Depending on the suspected cause, diagnosis may include:
- A complete scalp examination and evaluation of the eyebrows, eyelashes, nails, or other hair-bearing areas when appropriate
- A hair-pull test to determine whether active shedding is occurring
- Dermoscopy or trichoscopy, which uses magnification to examine hair shafts, follicle openings, and the scalp
- Clinical photographs to document density and monitor changes over time
- Blood tests to check for iron or nutritional deficiencies, thyroid disease, autoimmune conditions, or hormonal imbalances
- A fungal test or scalp scraping when an infection is suspected
- A scalp biopsy, in which a small tissue sample is examined under a microscope, when the diagnosis is uncertain or a scarring form of hair loss is possible
Not every patient needs every test. The evaluation is personalized based on whether the hair loss is diffuse or patchy, sudden or gradual, scarring or non-scarring, and whether other symptoms are present.
When Should You See a Dermatologist for Hair Loss?
Schedule a dermatology evaluation if you notice sudden or excessive shedding, new bald patches, a rapidly widening part, a receding hairline, eyebrow or eyelash loss, or hair loss that continues to worsen. Prompt care is especially important if the scalp is painful, itchy, inflamed, scaly, or developing smooth and shiny areas because some scarring forms of alopecia can cause permanent follicle damage. Early diagnosis can improve the opportunity to slow progression, address an underlying condition, and preserve existing hair.
How long will it take to re-grow my hair?
Hair growth is a very slow process. In the Anagen (growth) phase, hair will grow approximately 1 cm per month. Hair re-growth does not have a solid timeline that is true for all patients.