Alopecia disrupts nearly every component of the integumentary system, not just hair. The integumentary system includes your skin, hair, nails, oil glands, sweat glands, and the nerve endings embedded throughout. While hair loss is the most visible effect, the immune attack at the root of alopecia can alter nail structure, change how your skin regulates temperature, compromise its protective barriers, shift the microbial balance on your scalp, and even trigger pain in skin that looks perfectly normal on the surface.
What Happens Inside the Hair Follicle
Hair normally cycles through three phases: active growth (anagen), a brief transition (catagen), and a resting phase (telogen) before the strand sheds and a new one begins. In alopecia areata, the immune system attacks follicles during active growth, prematurely forcing them into the resting or transition phase. This cuts the growth cycle short, causing abrupt shedding with no healthy replacement strand waiting behind it.
The trigger is a breakdown in “immune privilege,” a protective status that normally keeps hair follicles invisible to the immune system. Stress, infections, or other triggers can strip that protection away. Once exposed, the follicle’s own cells become targets. Immune cells flood the area and release inflammatory signals that shut down the follicle’s growth machinery. Over time, repeated attacks cause the follicles to shrink, a process called miniaturization. Biopsies of chronically affected areas consistently show these miniaturized follicles, which produce thinner, shorter hairs or none at all.
Scarring vs. Non-Scarring: Two Different Fates for Skin
Not all forms of alopecia damage the integumentary system in the same way. Non-scarring types like alopecia areata alter the hair cycle but leave the follicle’s basic architecture intact. The follicle shrinks and goes dormant, but regrowth remains possible because the stem cells at the base survive.
Scarring (cicatricial) alopecia is fundamentally different. The inflammation destroys the hair follicle and its associated oil glands entirely, then replaces them with fibrous scar tissue. Histological studies of scarring alopecia consistently show perifollicular fibrosis (dense connective tissue encasing what’s left of the follicle), loss of sebaceous glands, and thinning of the outer skin layer. Once scar tissue fills in, that patch of skin is permanently altered. It loses its normal texture, can no longer produce oil, and will never grow hair again. The distinction matters: in non-scarring alopecia the integumentary system is disrupted but recoverable, while in scarring forms it is structurally remodeled.
Nail Changes in About 1 in 5 Patients
Because nails and hair follicles share a similar growth structure, the same immune attack that targets follicles often hits the nail matrix, the tissue beneath the cuticle where new nail cells form. On average, about 22% of people with alopecia areata develop visible nail changes, though reported rates range from 7% to 84% depending on disease severity.
The most common nail signs are pitting (tiny dents scattered across the nail surface), longitudinal ridging, trachyonychia (rough, sandpaper-textured nails), and leukonychia (white spots or lines). A red, mottled lunula, the half-moon shape at the base of the nail, is rarer but tends to signal more severe disease. People with alopecia totalis or universalis are more likely to have nail involvement, though nail changes occasionally appear on their own, without any hair loss at all.
How Oil and Sweat Glands Are Affected
In early alopecia areata, the follicle shrinks below the level of the sebaceous (oil) gland, but the gland itself is typically preserved. This means the skin surface in affected patches may still produce some oil, even though the hair is gone. Over time, though, chronic inflammation can reduce gland size and output, leaving the skin in those areas drier and less supple.
Scarring forms of alopecia tell a harsher story. Sebaceous glands are among the first casualties, destroyed alongside the follicle and replaced by scar tissue. Without oil glands, the affected skin loses its natural moisture barrier and becomes prone to dryness and irritation. Sweat glands sit deeper in the skin and are generally spared in most types of alopecia, so sweating ability in affected areas usually remains intact.
Lost Protection From Sun and Heat
Scalp hair is a surprisingly effective shield against solar radiation. Research from the Proceedings of the National Academy of Sciences found that hair significantly reduces the amount of thermal radiation reaching the scalp surface. Without it, the scalp absorbs far more solar energy. Bald men sweat from their scalp at two to three times the rate of men with hair, not because they’re hotter overall, but because the bare skin needs that much more evaporative cooling to compensate for the missing insulation.
This creates a double problem. The exposed scalp is more vulnerable to UV damage, increasing the risk of sunburn and long-term sun-related skin changes. At the same time, the body has to work harder to stay cool, losing more water through sweat in the process. For people with alopecia universalis, who lose hair everywhere, the loss of this protective layer extends beyond the scalp to any body surface that once had meaningful hair coverage.
Eye Risks When Lashes and Brows Are Gone
Eyelashes and eyebrows are functional parts of the integumentary system, not just cosmetic features. Lashes act as a physical filter, blocking sweat, dust, microorganisms, and even wind from reaching the eye’s surface. When alopecia causes complete loss of lashes and brows (a condition called madarosis), those barriers disappear. In one study, 44.3% of people who lost lashes and brows due to alopecia areata experienced some degree of eye problems, including dryness, surface inflammation, and blepharitis (irritation of the eyelid margins).
Scalp Pain Without Visible Damage
Many people with active hair loss report burning, stinging, or soreness on the scalp, a symptom known as trichodynia. The skin looks normal, but it hurts. This happens because of a signaling molecule called substance P, which nerve endings in the scalp release during inflammation. Substance P is involved in pain perception and also triggers local blood vessel dilation and immune activation, creating a feedback loop between the nervous system and the skin’s immune environment. Emotional stress can amplify this loop, which helps explain why many people notice their scalp pain worsens during periods of anxiety or tension. This represents a direct effect on the sensory nerve component of the integumentary system.
Shifts in the Scalp Microbiome
Healthy scalp skin hosts a balanced community of bacteria and fungi that help maintain the skin barrier. In people with alopecia areata, that balance shifts. Studies have found increased microbial diversity on affected scalp areas, which, counterintuitively, is not a good sign. A healthy scalp tends to have a stable, predictable community of microorganisms. Higher diversity can signal disruption.
Specific changes include altered ratios of common scalp bacteria. The proportion of certain Cutibacterium species relative to Staphylococcus species increases, and this shift becomes more pronounced with greater disease severity. In one analysis, the ratio of Cutibacterium to one Staphylococcus species jumped from about 1:1 in healthy controls to 16:1 in people with severe alopecia areata. Whether these microbial shifts are a cause or consequence of the disease is still being untangled, but they represent a measurable change to the skin’s living ecosystem.
Recovery and Regrowth Potential
Because non-scarring alopecia preserves follicle stem cells, the integumentary system retains the ability to recover. Modern treatments targeting the immune signaling pathways responsible for follicle attack have shown strong results. In one clinical study, 9 out of 12 patients with moderate-to-severe alopecia areata achieved an average of 92% hair regrowth within 3 to 6 months of treatment. Another study found that about 54% of patients reached at least 50% regrowth within three months on a different medication in the same drug class.
These treatments work by blocking the specific immune signals (through what’s called the JAK-STAT pathway) that drive the attack on follicles. When the inflammation stops, dormant follicles can re-enter their growth phase, and in many cases, hair, nail texture, and skin quality in affected areas gradually return to normal. For scarring alopecia, where the follicle and its glands have been replaced by scar tissue, the damage to the integumentary system is permanent and treatment focuses on stopping further progression rather than restoring what’s lost.