Eyebrow hair falling out can signal anything from a harmless phase of your natural hair cycle to an underlying health condition that needs attention. The medical term for eyebrow loss is madarosis, and it has dozens of possible causes, from thyroid problems and nutritional gaps to autoimmune conditions and chronic skin irritation. The pattern of loss, whether it’s patchy, concentrated on the outer edges, or spread evenly, often points toward the cause.
How the Eyebrow Growth Cycle Works
Eyebrow hairs follow a much shorter growth cycle than the hair on your scalp. The active growing phase lasts only 4 to 7 months (compared to several years for scalp hair), followed by a 2- to 3-week transition phase, then a resting phase of 3 to 4 months before the hair sheds naturally. Because this cycle is short, eyebrow hairs stay short and thick rather than growing long.
This means some eyebrow shedding is completely normal. You’re constantly losing and replacing individual hairs. The concern starts when you notice thinning that doesn’t fill back in, bald patches, or a change in overall density that wasn’t there before.
Thyroid Problems and the Outer Eyebrow
One of the most well-known causes of eyebrow loss is an underactive thyroid. When your thyroid gland doesn’t produce enough hormone, it slows metabolic processes throughout your body, including hair growth. It also causes a buildup of certain sugary molecules in the spaces between cells, which can thin or coarsen hair.
The hallmark pattern is loss of the outer third of the eyebrow, sometimes called the Queen Anne sign or Hertoghe sign. If you notice that the tail ends of your eyebrows are disappearing while the inner portions remain intact, thyroid dysfunction is one of the first things worth investigating. Other symptoms that often accompany it include fatigue, weight gain, cold sensitivity, dry skin, and a puffy face. The exact reason the outer third is affected first, rather than the whole brow, remains unexplained.
Autoimmune Conditions
Alopecia areata is an autoimmune condition where your immune system mistakenly attacks hair follicles. When it affects the eyebrows, it typically causes bilateral, patchy loss rather than the gradual thinning seen with thyroid issues. You might notice distinct bare spots on both brows, sometimes appearing suddenly.
Discoid lupus erythematosus, another autoimmune disorder, can cause redness, scaly patches, and hair loss on the eyelids and brows. In some cases, eyelash or eyebrow loss appears before other symptoms like skin plaques or scarring hair loss on the scalp. A rarer condition called Vogt-Koyanagi-Harada disease can cause depigmentation (whitening) of eyebrow and eyelash hairs along with vision problems.
The key difference with autoimmune eyebrow loss is that it tends to create distinct patches rather than uniform thinning, and it often affects both sides of the face.
Nutritional Deficiencies
Your eyebrow follicles need a steady supply of certain nutrients to maintain their growth cycle. The most commonly implicated deficiencies are iron, zinc, and biotin.
- Iron: Low iron stores are linked to a type of hair shedding called telogen effluvium, where hairs prematurely enter the resting phase and fall out. In a study of over 5,000 women, 59% of those with excessive hair loss had low iron stores, compared to a smaller proportion of women with normal hair.
- Zinc: Zinc supports hundreds of enzymes in the body, and deficiency is a recognized cause of hair loss. In one case report, a child with zinc-deficiency hair loss saw shedding stop within three weeks of starting a supplement.
- Biotin: This B vitamin serves as a building block for enzymes involved in hair structure. True biotin deficiency is uncommon but causes noticeable hair thinning when it occurs.
Nutritional causes are more likely if your diet is restricted, you’ve had significant weight loss, or you have a condition that impairs nutrient absorption.
Skin Conditions That Damage Follicles
Chronic inflammation on or around the eyebrows can damage hair follicles directly. Eczema, psoriasis, and seborrheic dermatitis can all affect the brow area, causing itching, flaking, and gradual hair thinning. Contact dermatitis from cosmetic products, brow tints, or skincare ingredients is another common culprit.
A condition called frontal fibrosing alopecia deserves special mention. It causes a slowly receding hairline and progressive eyebrow loss, and it’s becoming increasingly recognized. On the eyebrows, it shows characteristic red or gray dots where follicles once were. On the scalp, it causes scarring that permanently closes follicular openings. This type of loss is not reversible once scarring occurs, making early recognition important.
Physical Damage and Hair Pulling
Mechanical causes are more common than many people realize. Repeated tweezing, aggressive threading, or waxing can permanently damage follicles over time. Rubbing your brows habitually, whether from stress or irritation, can also thin them gradually.
Trichotillomania, a compulsive hair-pulling disorder, frequently targets the eyebrows. Under magnification, pulled eyebrow hairs show distinctive signs: broken hairs at different lengths, coiled hairs, hook-shaped hairs, and black dots where hairs have broken off at the surface. This pattern looks different from autoimmune patchy loss, though distinguishing between the two can be challenging, especially if the person doesn’t recognize or acknowledge the pulling habit.
Other Medical Causes
Several less common conditions can cause eyebrow loss. Chemotherapy affects rapidly dividing cells, including hair follicles, and often causes temporary eyebrow and eyelash thinning alongside scalp hair loss. Secondary syphilis and leprosy are infectious causes that historically were associated with eyebrow loss. Certain medications, including some blood thinners, retinoids, and hormonal contraceptives, can trigger hair shedding that includes the brows.
Aging also plays a role. Eyebrow hairs naturally become finer, lighter, and sparser with age, particularly after menopause in women. This is gradual and affects the entire brow rather than creating patches.
How Doctors Investigate Eyebrow Loss
If your eyebrow loss is noticeable or persistent, a doctor will typically start with a physical exam of the pattern and then order blood work. Common tests include thyroid-stimulating hormone (TSH) to check thyroid function, iron and ferritin levels to assess iron stores, a complete blood count, vitamin levels (including biotin and zinc), blood sugar, sex hormones, and an antinuclear antibody test to screen for autoimmune conditions. Inflammatory markers and cortisol levels may also be checked depending on your other symptoms.
The pattern of your eyebrow loss gives the doctor important clues before any test results come back. Outer-third thinning points toward thyroid issues. Patchy, bilateral loss suggests alopecia areata. Broken hairs at varying lengths suggest mechanical damage. Red or scaly skin around the brow suggests a dermatological cause.
Regrowth and Treatment
Whether your eyebrows grow back depends entirely on the cause. If the underlying issue is thyroid dysfunction, treating it with thyroid hormone replacement typically allows regrowth over several months. Nutritional deficiencies respond to supplementation, sometimes within weeks. Eyebrows lost to temporary stress or telogen effluvium usually recover on their own once the trigger resolves.
For autoimmune causes like alopecia areata, treatments focus on calming the immune response in the area. Results vary, and some people experience cycles of loss and regrowth.
For people with persistent thinning regardless of cause, a prescription topical solution originally developed for eyelash growth has shown strong results on eyebrows. In a clinical trial, about 78% of people applying it once daily saw measurable improvement in eyebrow fullness by month 7, compared to 43% using a placebo. Eyebrow darkness improved as early as one month, and fullness improvements appeared by month two. These gains were sustained throughout the treatment period.
When follicles have been permanently scarred, as with frontal fibrosing alopecia or long-term physical damage from over-plucking, regrowth is unlikely. In these cases, cosmetic options like microblading or eyebrow transplantation are the main paths forward.