Worried the upcoming season will come with a hair walkout? Seasonal hair shedding can be stressful, especially when seeing more hair than usual in your brush or shower drain. Is it normal to lose more hair in the Fall and Spring, or is it a sign of a deeper issue? We're here to break down the science of why different seasons trigger shedding, and why you may want to keep your plumber on speed dial.

Seasonal Hair Shedding Explained

What exactly is seasonal hair shedding? It’s an evolutionary phenomenon where your body follows a biological rhythm, triggering a shift in the natural hair growth cycle.
When seasonal changes in daylight and temperature occur, the body temporarily increases hair fall. It is essentially a mild, predictable form of telogen effluvium—a condition where a larger-than-normal percentage of hair follicles enter the "resting" phase simultaneously.  

How much hair loss is considered "normal" during a seasonal shift? At any given time, about 5-10% of hair is in the shedding phase, accounting for a typical daily loss of 50-100 hairs. However, during seasonal peaks, the amount can increase, jumping to 100-200 hairs per day, temporarily spiking that percentage. The good news is that seasonal shedding is a temporary condition that often resolves on its own within about 6 to 8 weeks and doesn’t reduce overall density in the long-term.

Why Seasonal Hair Shedding Happens

So, why does the promise of blooming flowers and sunshine coincide with more hair on your pillow? Like many things, it’s all about (seasonal) timing, coming down to a mix of biological and environmental cues that impact the hair growth cycle. Changes in weather and daylight trigger a biological shift in hair growth cycles, which can induce hair shedding. A couple of theories explain why seasonal hair fall takes place

• The Evolutionary Theory: Like other mammals that shed their winter coats, humans may have an ancestral "molting" cycle. Researchers suggest we retain hair in the Summer to protect our scalps from UV rays and in the Winter to provide warmth.  A "shedding event" occurs once those protections are no longer needed.
• The Melatonin Mystery: One prominent theory suggests that changes in daylight hours affect the production of melatonin—a key regulator of the hair growth cycle. While often associated with sleep, a drop in this vital hormone can signal follicles to move from the growth phase (anagen) into the resting phase (telogen).
  
  Winter stress, due to reduced sun exposure, triggers a shift in melatonin production, pushing more hairs essentially to “hibernate” like bears in winter. But, as we move from Winter to Summer and the days lengthen, our exposure to darkness decreases, reducing melatonin production. Less melatonin means more hair follicles shift into the shedding phase in Spring.
• A Parallel to Animals: Some experts relate seasonal hair shedding in humans to how certain animals shed their coats as temperatures rise. Hair has an insulating effect, but unlike animals, we don’t need a winter coat to stay warm. Think of it as nature helping you stay cooler during the warmer months, with temperature and environmental changes signaling the body to reset the hair cycle, leading to increased shedding.

When Shed Happens

What month does seasonal hair shedding usually start? Seasonal hair loss typically occurs in the Spring and then again in early Fall. And, while Spring is when tufts of Fido's and Fluffy's hair appear all over, Fall is a more significant time of year for seasonal hair shedding in humans.

• Autumn (The Major Peak): Why does hair shed more in the autumn specifically? As daylight decreases, most studies show that hair shedding is highest in September, October, and November, much like the falling leaves. This is when the hair that "rested" during the Summer falls out.
  
  Additionally, high exposure to UV rays and heat during July and August can stress the follicles, causing them to enter the resting phase prematurely. Since the resting phase lasts about 3 months, the fallout often manifests in October and November.
• Spring (The Minor Peak): A smaller spike in hair shedding is often observed in March and April as the body resets itself and adjusts to increasing daylight. Spring shedding may seem more noticeable, as the extra hours of daylight ruthlessly highlight thinning hair.

Environment + Seasonal Hair Shedding

Do people who live in different climates experience more or less seasonal hair shedding? People living in zones with distinct seasons may notice these seasonal shifts more than those living in climates with more consistent temperatures and humidity.

Can winter weather cause hair to fall out? Those who live in climates with harsh, dry air and the requisite indoor heating tend to have drier, brittle hair prone to breakage, which may mimic seasonal shedding.

Can changes in humidity and temperature trigger hair loss? Climates that become hot and muggy in the Spring and Summer may cause an imbalance of oil, yeast, and bacteria that can irritate and inflame follicles, triggering shedding in hairs near the end of their cycle. Rising temperatures and humidity can also cause strands to absorb moisture, swell, lift the cuticle, and become more elastic, which can increase breakage that’s easily mistaken for shedding.

Does lack of sunlight/Vitamin D in winter cause shedding? Cause it? No. Influence it? Potentially, yes. Vitamin D helps follicles re-enter the growth phase and supports immune balance around the follicles. More time spent indoors equals less UVB exposure and less natural vitamin D production. Chronically low vitamin D can disrupt the hair cycle, allowing more hairs to enter the resting phase and leading to shedding in early Spring.

Seasonal Shedding vs. Serious Hair Loss

How can I tell the difference between seasonal shedding and permanent hair loss?

Before panicking upon seeing more hair in the drain, determine if your shedding meets the criteria for seasonal hair thinning:

• Timing + Duration: How long does seasonal shedding typically last? It usually lasts 4 to 8 weeks and then stops on its own. In contrast, other forms of hair loss can resolve within 6 months, whereas more serious forms can be ongoing.
• Pattern: The shedding is diffuse (happening all over the head) rather than in specific patches or a receding hairline, with a white bulb present at the root of fallen hairs.
• Density: Hair is otherwise healthy, no widening of the part, thinning strands, or thin spots, as with other types of hair loss. You shouldn't see dramatic changes in your hair texture, volume, or scalp visibility.

Note: Seasonal shedding may coincide with the aftermath of a severe stressor you experienced a few months back and manifest similarly. If you had a significant emotional loss, trauma, or illness 1-3 months ago and are witnessing rapid, sudden shedding, that is a likely factor.

Who Is Most Affected

Does everyone experience seasonal shedding, or just some people? While shedding happens to many, those with genetic predispositions to hair thinning and certain hair types might notice the peaks in Spring and Fall more acutely. Let’s examine whether genetics and hair type can influence seasonal shedding.

• Genetics: Can genetics affect seasonal hair shedding? Aside from genetics determining whether you’re prone to conditions like androgenetic alopecia, our genes also dictate how many hair follicles we have, the length of our growth phase, and our hair’s sensitivity to hormonal shifts. Some people naturally experience noticeable seasonal shedding because their follicles are more responsive to light changes and hormone fluctuations. If your parents mention “Fall shedding,” there’s a decent chance you'll notice it, too.
• Hair type: Does hair type play a role in seasonal shedding? Your hair type doesn’t change how much you shed—but it may change how obvious it looks. So sometimes it’s not more shedding—it just looks like it, depending on the type of hair you have.
  • Fine hair: Shedding can look dramatic because strands and total volume are naturally thinner.
  • Thick hair: Hair shedding tends to be less noticeable because of overall thickness, yet those with dense hair may shed more total strands.
  • Curly hair: Recently shed strands get trapped and come out all at once during washing, making it seem excessive.
  • Long hair: Longer strands look like “more hair” even when it’s a normal amount.

What You Can Do

Can I stop seasonal hair shedding from happening? Sorry, but that would be like asking if you can stop a tidal wave. While you can’t stop seasonal hair shedding, there are steps you can take to help manage the situation. And, since seasonal shedding is self-limiting, it rarely requires medical treatment. The best strategy is to focus on a healthy hair and scalp environment to weather this seasonal change:

• Nourish from within: Maintain a balanced diet rich in essential nutrients and protein to support new hair growth. Proper hydration is also key.
• Stress less: Prioritizing stress management may be beneficial, as seasonal shifts can sometimes coincide with stressors, triggering increased shedding.
• Treat it right: Are there specific shampoos or scalp treatments that help? Yes, products that promote scalp health can help support your hair through this transition. A good plan is to use a balancing shampoo in the Spring and Summer, a moisturizing shampoo in the Fall and Winter, followed by a moisturizing conditioner and revitalizing scalp serum year-round to diminish shedding.
• Be gentle: Avoid excessive heat styling and practice gentle grooming techniques to minimize additional breakage and tension on follicles while your cycle is readjusting.
• Seek professional help: At what point should I see a dermatologist about my shedding? If shedding persists for more than a few months or you notice density changes, visible thinning patches, or an itchy/sore scalp, it's likely more than a seasonal hair issue and worth checking with a healthcare professional to rule out other potential factors.
  
  Can a blood test determine if my hair loss is just seasonal? Not exactly, but doctors can run labs to rule out internal triggers that mimic seasonal shedding, such as low iron, vitamin D, vitamin B12, or hormone levels, as well as thyroid issues. If labs are normal and your shedding matches a seasonal pattern, that supports the idea that it’s a temporary condition.

For the normal seasonal shed, remember: it's not a hair-pocalypse, it's just science!