Shedding: An updated guide to a common cause of hair loss

Triggers that disturb the hair’s normal cycle

Often, a clear cause of shedding cannot be identified in people with sudden (acute) telogen effluvium. Determining the cause of long-lasting (chronic) telogen effluvium can be even more difficult, but a careful review of the patient’s medical history and recent life events often helps uncover potential triggers. Many things can trigger hair shedding (Table 1):

• Acute or chronic medical illnesses such as febrile illness and systemic rheumatic disease (collagen vascular disease)¹⁰

• Major surgery¹

• Childbirth, miscarriage, abortion, or menopause¹¹

• Strong emotional stress¹

• Changes in diet (eg, diets designed for rapid weight loss, eating too little protein or calories, or having low levels of important nutrients such as iron, zinc, or vitamin D)¹¹

• Hormonal problems (eg, thyroid disorders, androgen excess)^11,12

• Certain medications or supplements (eg, vitamin A—as little as 25,000 IU daily may lead to hair shedding)¹³; see Table 2^11,13–16

• Exposure to toxins (eg, heavy metals)¹⁷

• Systemic infections (eg, COVID-19)¹⁸

• Scalp conditions such as dandruff or psoriasis

• Infections of the scalp.

Low vitamin D and iron levels have been proposed as possible contributors to telogen effluvium; however, current evidence remains insufficient to establish the underlying mechanism.^19–22

Patient history

The patient’s medical history is essential. It helps confirm that the pattern of hair loss is consistent with telogen effluvium, identify possible triggers, and rule out other causes of hair loss. Clinicians typically ask about the following:

• Course of hair loss: when the shedding began, how long it has lasted, and any possible triggering events

• Hair shedding features: estimated daily hair loss and the appearance of shed hairs

• Medical history: recent or chronic illnesses; major surgery; rapid weight loss; restrictive diets; recent childbirth, miscarriage, or abortion; iron-deficiency anemia; nutritional deficiencies (eg, iron, ferritin, zinc, protein, vitamin D); thyroid disease; and a review of systems to identify underlying conditions¹¹

• Psychological stressors

• Medication and supplement use

• Exposure history: possible toxic or chemical exposures

• Family history of hair or scalp disorders.

A detailed medical history can also point to a coexisting hair disorder or more than one contributing factor. In women, reviewing menstrual and reproductive history may help identify androgen-related hair loss or hormonal abnormalities.¹¹

Physical examination

Evaluation of hair loss includes careful examination of the scalp, hair, and nails.

Hair pull test

A gentle hair pull test may be performed to check for active hair shedding¹¹:

• Hold about 50 to 60 hairs close to the scalp

• Gently pull the hairs from the roots toward the ends

• Repeat this test in different areas of the scalp, such as the sides and front

• Examine the shed hairs under a microscope to confirm that they are telogen (resting) hairs, which have a small, club-shaped bulb at the root; other hair changes may suggest different hair conditions.

Finding 5 or more telogen hairs in 1 pull, or more than 15 telogen hairs after 3 pulls, supports a diagnosis of active telogen effluvium.¹¹

The hair pull test may give a false-negative result if the hair was washed or heavily groomed on the day of the examination. For best results, the test should be done 2 to 3 days after shampooing. On the other hand, a false-positive result can occur if the hair has not been washed or combed for several days.¹¹

Dermoscopy

Dermoscopic findings in telogen effluvium are generally nonspecific. In acute telogen effluvium, dermoscopy may reveal empty follicles and numerous upright regrowing hairs of normal thickness. Importantly, dermoscopy can aid in differentiating chronic telogen effluvium from female pattern hair loss, in which the diameter of the hair shafts typically varies more.^14,24

Wood’s light examination

A Wood’s (long-wave ultraviolet) light may help identify seborrheic dermatitis, which can be associated with telogen effluvium, and detect hyperpigmentation, a feature more suggestive of scarring hair loss.¹¹ In seborrheic dermatitis, scalp scales may become more visible and Malassezia yeast can fluoresce orange under ultraviolet light.²⁵

Scalp biopsy

Scalp biopsy can help distinguish telogen effluvium from other causes of hair loss. Biopsies are typically obtained using a 4-mm punch and include subcutaneous fat. Many dermatopathologists prefer taking 2 samples—1 vertically and 1 horizontally sectioned— to allow comprehensive follicular assessment. Samples should be taken from areas of hair thinning rather than complete alopecia, and bitemporal, frontal, and vertex scalp regions should be avoided to reduce overlap with androgenetic alopecia.¹¹

Additional tests

Less commonly used tests for telogen effluvium are usually performed in specialized hair clinics or research settings.¹¹

Screening laboratory evaluation

• Complete blood count to evaluate for anemia

• Comprehensive metabolic panel to screen for underlying systemic disease

• Thyroid-stimulating hormone to assess for thyroid dysfunction

• Ferritin to evaluate iron stores.

Additional laboratory testing is selected based on the patient’s history, symptoms, and physical findings. Further studies may be used to rule out other causes of hair loss, including nutritional deficiencies (especially 25-hydroxyvitamin D), toxin exposure, hormonal disorders, or autoimmune disease.^11,21,26

For example, a hormonal evaluation may be appropriate in women with signs of androgen excess, such as acne, virilization, or obesity. Testing for antinuclear antibodies may be considered when clinical features suggest an underlying immune-mediated disorder.¹¹

Address the underlying cause

Telogen effluvium often improves on its own, especially when triggered by a single event such as childbirth or illness. When hair shedding is caused by an ongoing factor, the trigger should be identified and treated, if possible (Table 3).¹ This may include managing associated medical conditions, correcting nutritional deficiencies, addressing psychological stressors, which may require therapy or other supportive interventions, stopping a suspected medication (with reassessment after at least 3 months), and treating other scalp conditions such as seborrheic dermatitis.^11,27

Psychological support and education

Hair loss can cause significant emotional distress, even when the amount of hair loss is small. Reassurance regarding the reversibility of the condition, empathetic communication, and patient education are key components of care. Patients benefit from a simple explanation of the hair growth cycle, emphasizing that telogen effluvium causes temporary shedding—not complete hair loss—and that regrowth typically becomes noticeable within 6 to 12 months once the trigger is removed or treated. Scheduled follow-up visits can help provide reassurance and identify patients with persistent shedding who may need further evaluation.^28,29

Cosmetic support

Cosmetic strategies can help reduce the visible impact of hair loss. These may include hairstyling techniques, hair coloring, scalp camouflage products, or hairpieces. Hair transplantation is not appropriate for telogen effluvium.¹¹

Medical treatments

The benefit of treatments such as topical minoxidil or nutritional supplements in patients without deficiencies is uncertain. Some clinicians use topical 5% minoxidil once daily, particularly in chronic telogen effluvium, to support hair density and regrowth, although strong evidence is lacking.¹¹ Patients should be counseled that results take months to assess and that shedding may temporarily increase when starting or stopping minoxidil.^2,30

Low-dose oral minoxidil (0.25–5.0 mg) has led to improvement in small retrospective studies of chronic telogen effluvium, but more research is needed.^31–33 Possible side effects include unwanted hair growth, low blood pressure, and swelling.³⁴

Minoxidil is not routinely recommended for acute telogen effluvium, particularly when a reversible trigger is identified or remains unaddressed, given limited evidence of benefit and the potential for unnecessary cost, burden, and false expectations. Counseling should instead emphasize reassurance, the often self-limited course, and correction of contributing factors.

Common nutritional supplementation

Iron supplementation is recommended for patients with iron-deficiency anemia.^2,35 Its use in patients without anemia remains controversial, though some clinicians aim to maintain ferritin levels within the higher end of the normal range based on clinical experience. The benefit of supplements such as zinc, biotin, or vitamin D in the absence of deficiency is unclear (although Sattar et al³⁶ reported positive results with vitamin D₃ in a study of 40 women in Pakistan), and their routine use is not supported by strong evidence.¹¹

Treatment of androgen-driven processes

Of note, early androgenetic alopecia can also present with increased shedding, and telogen effluvium is sometimes an early sign or unmasking of androgenetic alopecia rather than a completely separate condition. When androgenetic alopecia is identified as the cause of persistent hair loss, treatment should address the androgen-driven process with therapies such as spironolactone or finasteride, often together with minoxidil to support hair growth. Recognizing this overlap is important because hair loss may continue to progress if the underlying androgenetic alopecia is not treated.