Why Am I Losing Armpit Hair? Causes and When to Worry

Armpit hair loss usually comes down to one of a handful of causes, ranging from completely harmless age-related thinning to underlying hormonal or autoimmune conditions that deserve medical attention. The adrenal glands produce the androgens responsible for growing axillary hair in the first place, and anything that disrupts those hormones or damages the hair follicles locally can thin out the hair under your arms. The distinction between “nothing to worry about” and “see a doctor” often hinges on whether other symptoms tag along and how quickly the loss happens.

Aging and Declining Adrenal Androgens

Armpit hair exists because of a process that begins in childhood, when the adrenal glands start producing dehydroepiandrosterone (DHEA) and its sulfated form. This hormonal surge, which kicks in around age six to eight, is what eventually triggers the growth of both axillary and pubic hair in boys and girls alike. The process is sometimes called adrenarche, and it is essentially unique to humans and a few primate relatives.¹

The reason this matters for thinning armpit hair later in life is that adrenarche has a mirror image in aging. As you get older, adrenal androgen output gradually declines. Researchers have noted that a reversal of adrenarche appears to occur during the aging process, meaning the same hormonal engine that grew your armpit hair decades ago slowly winds down.¹ For many people, this is the most likely explanation for noticing thinner or sparser underarm hair in their forties, fifties, and beyond. The hair does not vanish overnight; it gradually miniaturizes and grows more slowly, much like what happens on the scalp with age. If you are middle-aged or older and the hair loss is gradual with no other symptoms, declining adrenal androgens are probably the culprit, and there is nothing medically alarming about it.

Repeated Hair Removal and Local Damage

If you have been shaving, waxing, or plucking your armpits for years, the hair removal itself may be contributing to what looks like hair loss. Every time you remove hair mechanically, you trigger a local inflammatory response. Research measuring skin reactions after different removal methods found that both plucking and waxing caused a significant rise in redness within 30 minutes, while shaving produced a notable spike in skin dryness.² Inflammatory markers like IL-1α rose after all three methods, with shavers showing the largest increase at roughly double their baseline levels.²

Individually, these inflammatory episodes resolve within a couple of days. But years of repeated cycles can accumulate. Chronic low-grade irritation at the follicle can weaken regrowth over time, and waxing and epilating physically yank the hair from the root, which can damage the follicle if done aggressively or on irritated skin. Laser hair removal and electrolysis go further by intentionally destroying the follicle. So if you have a long history of regular armpit hair removal and now notice that regrowth is finer or patchier than it used to be, the removal habit may be partly responsible. This is not a health concern, though it is worth knowing so you do not mistake a cosmetic result for a medical symptom.

Alopecia Areata

When armpit hair loss is patchy, sudden, or accompanied by hair loss elsewhere on the body, alopecia areata becomes a real possibility. This is a chronic, immune-mediated condition where the body’s own immune system attacks hair follicles.³ Most people associate it with round bald spots on the scalp, but the condition can affect any hair-bearing site on the body, including the armpits, pubic area, eyebrows, and eyelashes.⁴

The clinical spectrum is wide. At one end is patchy alopecia areata, which might show up as a single smooth bald patch under one arm. At the other end are alopecia totalis, involving the entire scalp, and alopecia universalis, which strips all body hair including axillary and pubic hair.⁴ Hair loss in alopecia areata is non-scarring, meaning the follicles are not permanently destroyed, and regrowth is possible, though recurrence is unpredictable.⁵

A few clues suggest alopecia areata rather than other causes. The affected skin typically looks smooth and normal rather than red, scaly, or scarred. The patches tend to appear suddenly rather than thinning gradually over months. And you may notice similar patches on the scalp, beard, or other body sites at the same time. If this pattern sounds familiar, a dermatologist can usually confirm the diagnosis with a visual exam and sometimes a skin biopsy.

The Emotional Weight of Body Hair Loss

It is easy to assume that losing armpit hair is purely a cosmetic issue, especially in a culture where many people remove it voluntarily. But for people experiencing involuntary hair loss from conditions like alopecia areata, the experience can be surprisingly distressing. A qualitative study of 45 patients with alopecia areata found that people described their diagnosis as “devastating,” with nearly half reporting feelings of sadness or depression and a large proportion feeling anxious about being judged by others.⁶

Patients in the study reported feelings of helplessness driven by the unpredictability of the disease, never knowing when hair might fall out again or grow back.⁶ This matters because people who notice their armpit hair disappearing sometimes downplay it or feel silly bringing it up to a doctor. The loss of body hair you cannot even see in a mirror might seem trivial, but it can signal a condition that affects your wellbeing in ways that go beyond appearance, and it deserves the same medical attention as any other unexplained symptom.

Thyroid Dysfunction

Both an overactive and an underactive thyroid can cause widespread hair shedding, and the armpits are not exempt. Thyroid hormones help regulate the hair growth cycle across the entire body, so when they are out of balance, hair can enter its resting phase prematurely and fall out in larger-than-normal amounts.⁷ This type of shedding tends to be diffuse rather than patchy, meaning the hair thins all over rather than falling out in discrete spots.

Thyroid-related hair loss often comes alongside other symptoms that make the picture clearer. With hypothyroidism, you might notice fatigue, weight gain, dry skin, and feeling cold all the time. With hyperthyroidism, the pattern flips toward weight loss, a racing heartbeat, and feeling overheated. Medications used to treat thyroid disorders can themselves contribute to hair shedding as well.⁷ If you are losing armpit hair alongside scalp hair and experiencing any of these systemic symptoms, a simple blood test for thyroid function is one of the first things a doctor will order.

Adrenal Insufficiency and Addison’s Disease

The connection between the adrenal glands and armpit hair goes deeper than the gradual decline of aging. When the adrenal glands fail outright, as in Addison’s disease, axillary and pubic hair can disappear almost completely. Early case reports documented women with Addison’s disease who had near-total absence of body hair below the scalp and eyebrows, despite otherwise normal menstrual function.⁸ This observation was actually one of the early clues that axillary and pubic hair in women depend on adrenal hormones rather than on the estrogens produced by the ovaries.⁹

Addison’s disease is uncommon, but its hallmark is insufficient production of cortisol and aldosterone, along with the adrenal androgens that maintain body hair. Other symptoms tend to be hard to miss: extreme fatigue, darkening of the skin (especially in skin creases and on the gums), low blood pressure, salt cravings, and sometimes nausea or abdominal pain. If axillary hair loss is your only symptom, Addison’s disease is very unlikely. But if you are also dealing with unexplained exhaustion and skin changes, the hair loss becomes a useful piece of the diagnostic puzzle.

Pituitary Gland Problems

The pituitary gland sits at the top of the hormonal chain of command, sending signals that tell the adrenal glands, thyroid, and gonads how much hormone to produce. When the pituitary underperforms, a condition called hypopituitarism, the downstream effects can ripple across multiple organ systems at once. One of those effects is loss of body hair, including armpit and pubic hair, because the adrenal glands and gonads are no longer receiving the hormonal instructions they need to support hair growth.

Pituitary dysfunction can result from tumors (most commonly pituitary adenomas), surgery, radiation therapy to the head, or autoimmune inflammation of the gland. The hair loss in these cases is rarely the first or only symptom. You would typically also see changes in menstrual cycles or libido, unusual fatigue, sensitivity to cold, or in some cases visual field changes if a growing tumor presses on the optic nerves. The skin itself may become paler and finer. Because the pituitary controls so many hormonal axes, the symptom constellation tends to be broader and more complex than what you would see with an isolated adrenal or thyroid issue.

Other Medical Causes Worth Knowing About

A few additional conditions can lead to armpit hair loss, though they are less common:

Telogen effluvium: A period of severe physical or emotional stress, major surgery, high fever, or rapid weight loss can push large numbers of hair follicles into a resting phase simultaneously. The shedding is diffuse, temporary, and usually resolves on its own within several months once the triggering event passes.
Nutritional deficiencies: Iron deficiency, severe protein malnutrition, and zinc deficiency have all been linked to hair thinning across the body. These are more likely in people with restrictive diets, malabsorption disorders, or chronic illness.
Medications: Chemotherapy is the most obvious drug-related cause of body-wide hair loss, but blood thinners, certain antidepressants, beta-blockers, and hormonal medications can also thin body hair as a side effect. If the timing of your armpit hair loss lines up with starting a new medication, the connection is worth raising with your prescriber.
Diabetes: Poorly controlled diabetes can affect circulation and hormone regulation, sometimes leading to reduced body hair. This tends to be gradual and accompanied by other well-known diabetes symptoms like increased thirst, frequent urination, and slow wound healing.

None of these conditions would typically present with armpit hair loss as the sole symptom, which is why context matters so much when deciding whether to worry.

How Doctors Evaluate Unexplained Hair Loss

There is no single standard battery of lab tests that every doctor orders when you walk in with hair loss. The workup is guided almost entirely by what else is going on: your other symptoms, how quickly the loss happened, where on the body it occurred, and what the affected skin looks like.¹⁰ This means the history you provide is genuinely important. A doctor evaluating armpit hair loss will want to know whether it came on suddenly or gradually, whether you have noticed hair loss anywhere else, and whether you have any other symptoms like fatigue, weight changes, or skin darkening.

Based on that conversation, common first-line tests include thyroid function (TSH), a complete blood count, iron studies, and sometimes adrenal or pituitary hormone levels like DHEA-S and cortisol. If the pattern looks autoimmune, a dermatologist may examine the skin under magnification or take a small biopsy. The good news is that most of these causes are diagnosable with straightforward blood work and a careful exam.

When Armpit Hair Loss Is Just Fine

Given the list of possible medical causes, it is worth stepping back and acknowledging that most people who notice thinner armpit hair do not have a serious underlying condition. If you are over 40 and the thinning has been gradual, age-related hormonal decline is the most common explanation. If you have been waxing or shaving your armpits regularly for decades, follicle fatigue from mechanical removal could be a factor. And some people simply have genetically less body hair than others, which becomes more noticeable in certain areas as they age.

The situations that warrant a doctor’s visit are the ones where the hair loss is sudden, patchy, or accompanied by other changes. Smooth, round bald patches suggest alopecia areata. Hair loss across the scalp, eyebrows, and body paired with fatigue points toward thyroid or adrenal problems. Unexplained weight changes, skin darkening, dizziness, or menstrual irregularities alongside the hair loss elevate the concern further. In those cases, the armpit hair is a visible clue to something systemic, and getting a workup done early gives you the best shot at effective treatment. For everything else, the hair under your arms is simply following the same trajectory as the rest of your body, thinning a bit with time and doing nothing that needs fixing.

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PubMed. Adrenarche – physiology, biochemistry and human disease
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PubMed Central. The impact of different hair‐removal behaviours on the biophysical and biochemical characteristics of female axillary skin
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Nature Reviews Disease Primers. Alopecia areata
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SpringerOpen / PubMed Central. ‘You lose your hair, what’s the big deal?’ I was so embarrassed, I was so self-conscious, I was so depressed: a qualitative interview study to understand the psychosocial burden of alopecia areata
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PubMed Central. Impact of Thyroid Dysfunction on Hair Disorders
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The Journal of Clinical Endocrinology & Metabolism. Addison’s Disease Associated with Pubic and Axillary Alopecia and Normal Menses
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