Dermatologists—specialists in skin, hair, and nails—use various methods to diagnose different types of alopecia. These may include a physical examination, blood tests, scalp biopsy, and specialized tools such as dermatoscopes or ultraviolet (UV) light. The goal is to determine the specific type of hair loss, whether it is scarring or non-scarring, environmental or hereditary, and to rule out other potential causes of hair loss.

Physical Exam

During a physical examination, healthcare providers may apply several diagnostic tools to examine the scalp and hair condition.

dermoscopy
A dermatoscope is a magnifying tool used to examine the scalp’s surface. Sometimes, individual hairs are removed and examined under a microscope.

hair pull test
A gentle tug is applied to a small group of hairs to see how many come out. If more than 10% of hairs are pulled out, it may indicate alopecia.

wood’s lamp exam
Using UV light, this test checks for fluorescent areas that may indicate a fungal infection like tinea capitis.

These tests help distinguish between:

non-scarring alopecia
Hair follicles remain intact, and regrowth is possible. This is the most common form, although hair may not regrow in some cases, such as with androgenetic alopecia.

scarring alopecia
Hair follicles are permanently damaged, and scar tissue forms, preventing regrowth.

The exam also helps identify the pattern of hair loss, which varies depending on the type of alopecia.

Alopecia Areata

This non-scarring form of alopecia is likely triggered by an autoimmune reaction. It can affect any part of the body where hair grows.

physical signs may include:

  • Broken hair shafts

  • Black or yellow dots on the scalp

  • Patchy, coin-sized bald spots

  • Point hairs (thinner at the root)

  • Nail pitting (tiny indentations in nails)

  • Vellus hairs (light, short, soft hairs)

Frontal Fibrosing Alopecia

This type involves the immune system attacking hair follicles, resulting in scarring and a gradual receding hairline with patchy hair loss.

common indicators include:

  • Facial papules (pimple-like bumps)

  • “Lonely hair” sign (single hairs isolated at the front)

  • Partial or complete eyebrow hair loss

  • Redness and scaling around follicles (perifollicular erythema)

  • Scalp symptoms like itching, burning, or tenderness

Trichotillomania

This is a non-scarring type of alopecia resulting from compulsive hair pulling. It is both a dermatologic and psychiatric condition, often diagnosed by a dermatologist or mental health professional.

diagnostic criteria include:

  • Persistent urge to pull out hair

  • Hair loss across multiple body areas

  • Uneven hair patterns depending on pulling behavior

  • Varying hair lengths or broken ends

Medical History

A detailed medical history is essential for identifying the underlying cause of hair loss. A provider may inquire about:

important areas include:

  • Accompanying symptoms beyond hair loss

  • Changes in diet

  • Regular hairstyles and haircare practices

  • Family history of hair loss

  • Emotional or physical stress

  • Past illnesses or surgeries

  • Hair loss in other body areas

  • Hair product usage (e.g., heat styling, shampoos)

This history helps differentiate between:

anagen effluvium
Hair loss that begins within two weeks of chemotherapy treatment.

androgenetic alopecia
Hereditary hair loss marked by gradual thinning and family history. Women may show ponytail thinning; men may have variable hair thickness and yellowish scalp dots.

telogen effluvium
Triggered by stress, childbirth, or dietary changes. Hair loss is diffuse and non-patterned.

traction alopecia
Results from prolonged tension on the hair shaft due to hairstyles or products.

Scalp Biopsy

This minor procedure involves removing a small scalp sample (around 4 mm) under local anesthesia. A dermatopathologist analyzes the tissue to confirm the diagnosis.

a biopsy can help detect:

  • Inflammation, confirming alopecia areata

  • Scar tissue and inflammatory signs in scarring alopecia

  • Behavioral hair loss in trichotillomania (if denied by the patient)

Blood Tests

Blood tests help confirm alopecia or rule out other conditions that could cause hair loss.

common tests include:

  • complete blood count (CBC): Screens for anemia

  • sex hormone levels: Imbalances may contribute to alopecia

  • thyroid function: Elevated or low thyroid-stimulating hormone (TSH) can impact hair health

  • vitamin and mineral levels: Deficiencies in biotin, iron, or zinc may cause hair loss

A Quick Review

Diagnosing alopecia involves physical examination techniques like dermoscopy, UV light, and hair pull tests. A complete medical history helps link lifestyle or hereditary causes to hair loss. In some cases, a scalp biopsy or blood tests may be necessary to make an accurate diagnosis and develop a treatment plan.