Thinning hair on the sides of your head usually points to one of a handful of causes: repeated tension from hairstyling, hormonal shifts, an autoimmune condition called frontal fibrosing alopecia, or nutritional gaps like low iron. The sides and temples are particularly vulnerable because the hair follicles there are finer and shallower than those on the crown, making them quicker to show damage. Figuring out which cause applies to you depends on the pattern of loss, your age, and a few other clues worth understanding.
Traction Alopecia: The Most Common Styling Cause
If you regularly wear tight ponytails, braids, cornrows, buns, extensions, or wigs pinned over braids, the steady pull on your hairline can damage follicles permanently over time. This is traction alopecia, and the sides and temples are almost always the first areas affected because that’s where tension concentrates. Early signs include thinning along the hairline, redness or swelling on the scalp, and sometimes small bumps where follicles are inflamed.
The risk goes up with styles that require frequent re-tightening, like dreadlocks or weaves, and with anything that scrapes hair back tightly off the face. Even headgear worn for long periods, such as helmets or tightly pinned caps, can contribute. The good news is that traction alopecia caught early is reversible. Once the tension stops, follicles can recover. But years of repeated damage leads to scarring, and scarred follicles don’t grow hair back.
Hormonal Changes and Menopause
Throughout your reproductive years, estrogen helps protect hair follicles from the effects of androgens (the hormones more associated with male-pattern balding). When estrogen drops, whether from menopause, perimenopause, or conditions like polycystic ovary syndrome, the balance tips. Androgens become relatively more active, and follicles that are sensitive to them begin to miniaturize, producing thinner and shorter hairs before eventually going dormant.
In most women, this hormonal thinning shows up as diffuse loss across the crown and part line. But in more pronounced cases, particularly when androgen levels are significantly elevated, the temples and sides thin visibly too. Bitemporal recession in a woman, where the hairline pulls back at both temples, can sometimes signal an androgen-producing condition that’s worth investigating with blood work. The average age of menopause is around 51, and many women notice accelerated thinning in the years surrounding it.
Frontal Fibrosing Alopecia
Frontal fibrosing alopecia (FFA) is an autoimmune condition that’s become increasingly common in recent decades, especially in postmenopausal women, though it can appear as early as your 30s. It causes a slow, band-like recession of the hairline starting at the front, the temples, or both. The hair loss creates a visible strip of lighter, smoother skin along the forehead and sides where hair used to grow.
A few features distinguish FFA from other causes. Many people notice their eyebrows thinning or disappearing along the outer edges before the hairline visibly recedes. Scalp discomfort, either itching or a mild burning sensation, often precedes noticeable hair loss. Some people develop a rash of small bumps on the scalp that may be red, skin-colored, or yellowish and feel scaly. The loss from FFA is scarring, meaning affected follicles are permanently destroyed, so early diagnosis matters.
Thyroid Disorders
Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can disrupt the hair growth cycle. Thyroid-related hair loss typically appears as diffuse thinning across the entire scalp rather than in one specific spot. But because the hair on your sides and temples is naturally finer, overall thinning can look most dramatic there first.
The mechanism is telogen effluvium: thyroid imbalance pushes a larger-than-normal percentage of your hair into its resting phase at once, and those hairs eventually fall out. You might notice excessive shedding when washing or brushing. Other body hair can thin too, including eyebrows, eyelashes, and underarm hair. The reassuring part is that thyroid-related hair loss is typically reversible once hormone levels are brought back to normal with treatment.
Low Iron and Nutritional Gaps
Iron deficiency is one of the most underrecognized causes of hair thinning in women, partly because your iron can be low enough to affect your hair long before it’s low enough to cause anemia. Research suggests that ferritin (your body’s stored iron) needs to be at or above 70 micrograms per liter to sustain a healthy hair growth cycle. Many labs flag ferritin as “normal” at levels as low as 12 or 20, which means you could get a result in the technically normal range that’s still too low for your hair.
Women who menstruate heavily, follow restrictive diets, or have recently lost a significant amount of weight are at the highest risk. Other nutritional deficiencies linked to hair thinning include vitamin D, zinc, and B12, though iron tends to be the most impactful for hair specifically.
How Doctors Figure Out the Cause
A dermatologist will typically start with a close physical examination of your scalp, looking at the pattern of loss, the condition of remaining hairs, and whether there’s any scarring, redness, or scaling. They may perform a hair pull test, gently tugging a small section to see how many hairs come out easily.
Blood work is the next step if the cause isn’t obvious from the exam alone. The most commonly ordered tests include ferritin (iron stores), thyroid-stimulating hormone (TSH), and androgen levels. If a fungal infection is suspected, a scraping or swab of the scalp can be sent for culture. In cases where the diagnosis is still uncertain, particularly when scarring conditions like FFA are possible, a small punch biopsy of the scalp provides a definitive answer. The biopsy uses a pencil-sized device to take a tiny tissue sample for lab analysis.
Protecting the Hair You Have
Regardless of the underlying cause, reducing mechanical stress on your temples and sides gives follicles the best chance of recovery or preservation. The highest-risk styles are tight ponytails, weaves, tight buns, extensions, and cornrows or dreadlocks made with braids. If you need to tie your hair back, keep it loose. Messy buns and low, relaxed ponytails put far less strain on the hairline than sleek, pulled-back styles. Avoid backcombing to create volume, as this damages hair shafts and weakens already-vulnerable areas.
For hormonal or nutritional causes, treatment targets the root issue. Correcting a thyroid imbalance, replenishing iron stores, or addressing androgen excess can slow or reverse thinning over several months. Topical treatments that stimulate follicle activity are also an option for many types of female hair loss, and your dermatologist can help determine whether they’re appropriate for your specific pattern. Hair regrowth is a slow process regardless of the approach. Most treatments require four to six months of consistent use before visible improvement begins, so patience and early intervention both work in your favor.