Thinning hair on the sides of the head in men is most often the early stage of male pattern baldness, which typically begins with recession at the temples before progressing further. But it’s not the only explanation. Several other conditions, from autoimmune hair loss to mechanical damage from headgear, can thin hair specifically in this area. The cause matters because it determines whether the thinning is reversible.
Male Pattern Baldness and the Temples
Male pattern baldness (androgenetic alopecia) is by far the most common reason men lose hair on the sides. It follows a predictable sequence: thinning starts at the temples, creating triangular areas of recession on both sides of the hairline, then gradually moves toward the crown. The areas affected by balding have higher concentrations of androgen receptors and more of the enzyme that converts testosterone into DHT, a more potent hormone that shrinks hair follicles over time.
DHT shortens the growth phase of the hair cycle. Each time a follicle cycles through growth and rest, the new hair comes in thinner and shorter than the last. Eventually, follicles shrink so much that hairs can’t even break through the skin’s surface. This process, called follicular miniaturization, is why thinning on the sides often looks like the hairline is creeping backward rather than hair falling out in clumps.
The Hamilton-Norwood scale, which dermatologists use to classify male hair loss, dedicates its earliest stages to exactly what you’re seeing. Type II describes symmetrical triangular recession at the temples. Type III, considered the minimum threshold for clinical baldness, involves deep recession at the temples with visibly sparse coverage. If your thinning is limited to the sides and hasn’t reached the crown, you’re likely in the early stages, which is actually the best window for treatment.
Retrograde Alopecia: Thinning From Below
A less well-known pattern called retrograde alopecia works in the opposite direction from typical male pattern baldness. Instead of starting at the temples and moving backward, it begins at the nape of the neck and progresses upward toward the crown. It can also extend to the temples, causing noticeable thinning on the sides that looks different from the classic receding hairline.
This distinction matters most for men considering hair transplant surgery, because retrograde alopecia affects the “donor zone,” the area at the back and sides of the scalp where transplant grafts are typically harvested. Dermatologists diagnose it through visual examination, dermoscopy, hair density testing, and sometimes a scalp biopsy. If you’re thinning on both the sides and the lower back of your scalp, retrograde alopecia is worth investigating.
Autoimmune Hair Loss on the Sides
Alopecia areata is an autoimmune condition where your immune system attacks hair follicles. It usually causes round, smooth patches of hair loss, but one subtype called ophiasis specifically targets the sides and back of the head. The name comes from the Greek word for snake, because the hair loss forms a band-like pattern that wraps around the lower scalp, particularly above the ears.
The key difference between ophiasis and male pattern baldness is speed and appearance. Male pattern baldness develops gradually over months or years, with hairs thinning before disappearing. Ophiasis can appear relatively abruptly, and the affected skin is often completely smooth rather than covered in fine, miniaturized hairs. Thinning behind the ears is a particularly telling sign, since male pattern baldness rarely affects that area.
Ophiasis has a poorer prognosis than other forms of alopecia areata and often resists standard treatments like corticosteroid injections and topical therapies. If your side thinning appeared suddenly and in a band-like pattern, a dermatologist can distinguish it from pattern baldness with a close examination.
Mechanical Causes: Headgear and Tight Styles
Traction alopecia results from prolonged or repeated tension on hair follicles. In men, the most common culprits are tight hairstyles (braids, cornrows, dreadlocks, man buns pulled tightly) and headgear worn regularly. Military personnel, Sikh men who wear turbans, and anyone who routinely wears tight-fitting helmets or hats can develop thinning along the frontal, temporal, and parietal scalp, exactly the sides of the head.
The damage comes from the physical pulling force on the follicle, not from the hair being covered. Chemical treatments like relaxers or frequent heat styling don’t cause traction alopecia on their own, but they weaken the hair shaft and make it much more vulnerable to breakage when tension is added. If your thinning lines up with where a helmet strap sits, where a hat grips, or where your hairstyle pulls tightest, traction is a likely contributor.
Caught early, traction alopecia is reversible once the source of tension is removed. Left too long, the follicular damage becomes permanent. If you notice soreness, small bumps, or broken hairs along with the thinning, those are signs the follicles are under active stress.
Stress, Illness, and Diffuse Shedding
Telogen effluvium is a temporary form of hair shedding triggered by physical or emotional stress, illness, surgery, rapid weight loss, or nutritional deficiencies. It typically causes diffuse thinning across the entire scalp rather than targeting specific areas. However, some men notice it more on the sides simply because the hair there is shorter and offers less coverage to begin with.
One distinguishing feature of telogen effluvium is that it preserves the frontal hairline. Your hairline doesn’t recede; instead, you notice more hair falling out overall. The shedding usually begins two to three months after the triggering event and resolves on its own within six to nine months once the cause is addressed. If your thinning on the sides coincided with a stressful period or health change, this is a likely explanation, and the hair will typically grow back.
More prominent thinning behind the ears, though, may point toward diffuse alopecia areata rather than telogen effluvium. The distinction requires a dermatologist’s evaluation, but the location of the thinning is an important clue.
Scalp Conditions That Worsen Thinning
Seborrheic dermatitis, a common inflammatory scalp condition that causes flaking, redness, and itching, doesn’t directly destroy hair follicles. But chronic scratching in affected areas can lead to hair shedding and thinning over time. If your sides are itchy, flaky, or red alongside the thinning, the inflammation may be contributing to the problem. Treating the underlying dermatitis typically allows the hair to recover, since the follicles themselves remain intact.
What Actually Works for Regrowth
For male pattern baldness, minoxidil (the active ingredient in Rogaine) is one of the most accessible treatments. Applied topically, it can stabilize hair density and promote regrowth in the frontotemporal and vertex areas. Results aren’t instant: visible improvements typically appear between 9 and 16 weeks, with continued gains through 24 weeks of consistent use. One long-term study found that using 5% minoxidil foam for two years stabilized hair density, width, and scalp coverage in both the temples and crown.
The success rate varies. Studies show anywhere from about one-quarter to three-quarters of users experience measurable regrowth, depending on the formulation and how it’s combined with other treatments. The earlier you start, the better the odds. Minoxidil is most effective at maintaining existing hair and regrowing recently miniaturized follicles. Once a follicle has been dormant for years, no topical treatment is likely to revive it.
For traction alopecia, the treatment is removing the source of tension. For autoimmune-related loss like ophiasis, treatment options are more limited and typically involve working with a dermatologist on immune-modulating therapies. And for telogen effluvium, the best approach is addressing the underlying trigger, whether that’s nutritional, hormonal, or stress-related, and giving it time.
If you’re unsure which category your thinning falls into, the pattern itself is the best first clue. Gradual recession at the temples points to male pattern baldness. Band-like loss above the ears suggests an autoimmune cause. Thinning that follows the line of a hat or hairstyle suggests traction. And diffuse shedding after a stressful event suggests telogen effluvium. A dermatologist can confirm the diagnosis with a close examination and, if needed, a scalp biopsy.