What Causes Hair Loss in the Summer? How Sun Exposure, Heat, Humidity & Other Environmental Factors Play a Role

The long, hot days of summer have their pros and cons; the pros are vacations, a slower pace of life and loads of sunshine. Bugs, sticky weather and crowds are a few of the cons—including hair shedding and hair loss. While hair loss of any kind can be upsetting, studies show that shedding more hair during the summer months is a natural phenomenon, and common around the globe. Read on to find out about the underlying causes of summer hair loss, what the scientific research says, plus smart and effective ways to protect your hair during the warmer months.

The Science Behind Seasonal Hair Shedding

The hair growth cycle consists of four distinct stages: anagen, catagen, telogen, and exogen. During the anagen phase, hair actively grows, a process that can last for several years. The catagen phase follows, marking a short transitional period where growth slows, and the follicle prepares to rest. The telogen phase is the resting stage, during which the hair remains in place but is no longer actively growing. Finally, in the exogen phase, the hair naturally sheds to make way for new growth.

A larger proportion of hair follicles enter the telogen phase during certain times of the year, particularly in summer. This normal biological process is thought to be influenced by longer days and warmer temperatures, plus hormonal changes that are also triggered by these environmental shifts, so the shedding isn’t a sign of illness or permanent hair loss. Instead, it simply reflects the body’s cyclical adjustment to the season.

Why Does Hair Loss Increase in Summer?

Several factors make summer a peak period for hair shedding. One of the main contributors is the effect of sunlight on hormone production. When the days are longer you produce less melatonin, the hormone that affects the sleep /wake cycle. Melatonin influences the hair growth cycle as well, so when levels drop, more follicles may transition into the resting stage, leading to greater shedding. In addition, testosterone levels, which can rise during summer, have been associated with hair thinning in both men and women, further contributing to the issue.

UV radiation from the sun also plays a significant role. Ultraviolet rays penetrate the hair shaft, which can break down its protein structure and weakening its integrity, leading to hair loss and shedding. Prolonged sun exposure also depletes natural scalp oils, leaving both the scalp and hair dry and brittle and more prone to breakage and shedding.

Then there are the things that make summer, summer: high humidity, sweat, and swimming in chlorinated pools or saltwater. Sweat and salt can irritate the scalp, while chlorine strips away protective oils and damages the hair cuticle. Combine all these elements and you have a perfect storm for hair loss and shedding during the summer months.

What Research Says: Key Findings on Seasonal Hair Loss

Scientific studies have consistently shown that hair shedding follows a seasonal pattern. The landmark study by Kunz and colleagues in 2009 analyzed the hair cycles of over 800 healthy women across six years. The findings revealed a distinct annual rhythm, with the highest rates of telogen phase hairs occurring in late summer and early autumn. A secondary, smaller peak was observed in spring, while the lowest shedding rates were recorded in late winter.

Another study conducted on Chinese subjects in 2014 observed a mild increase in shedding during late summer, though the variation was less pronounced than in European populations. This suggests that seasonal shedding patterns may vary across different ethnic groups but still follow a similar trend.

Population-level data from Google Trends has also supported these findings. Analyses of search queries related to hair loss from 2004 to 2020 revealed spikes in public concern during July, August, and September, aligning with clinical observations. These studies collectively demonstrate that seasonal shedding is a widespread, natural phenomenon.

So, Is Summer Hair Loss Normal?

Yes!  Hair loss and shedding in summer is both a normal and temporary process, and experts agree that it shouldn’t be mistaken for a chronic condition. Think about it this way —just like some animals shed their coats in the summer (hello cat and dog fur!), humans experience similar cycles where hair is shed more noticeably during certain times of the year. Importantly, the hair lost during this period is replaced by new growth in the months that follow. So, while summer hair shedding may feel alarming, it typically resolves without intervention.

Additional Triggers That Worsen Summer Hair Loss

Still, several factors can make the situation worse. Nutritional deficiencies, specifically a lack of key vitamins and minerals such as biotin, iron, and vitamin D, can weaken hair and lead to more noticeable loss. Stress also has a profound impact on the hair growth cycle. Both physical stress, such as illness, and emotional stress can disrupt the cycle and push more hairs into the shedding phase.

Scalp infections or conditions such as seborrheic dermatitis can also exacerbate shedding. These conditions cause inflammation that affects the hair follicles. Exposure to harsh chemicals from swimming pools or certain hair treatments can weaken the hair structure. When these factors coincide with the natural seasonal shedding period, hair loss may appear more dramatic than it is.

How to Prevent and Minimize Summer Hair Loss

While you can’t completely prevent seasonal shedding, you can take steps to reduce its impact. Protecting your hair from the sun is one of the best places to start. Wearing hats and using hair products with UV filters are a very effective way to shield your strands from damage. Research on sun protection products shows they significantly reduce the oxidative stress and protein breakdown caused by UV radiation.

Maintaining proper hydration and nutrition is equally important. Consuming foods rich in essential nutrients supports hair strength from within. Leafy greens, nuts, seeds, fish, eggs, and lean meats provide biotin, omega-3 fatty acids, and proteins that are vital for healthy hair growth. Drinking enough water helps maintain scalp hydration and prevents dryness.

Proper hair care practices also go a long way in minimizing shedding. Use moisturizing shampoos and conditioners to restore moisture lost to heat and sun exposure. Avoid frequent use of heat-styling tools or use them on lower settings with heat protectants. After swimming, rinse your hair thoroughly to remove chlorine and saltwater, which can otherwise cause damage.

Lastly, scalp care is essential. Keeping the scalp clean and free from buildup helps prevent inflammation and promotes a healthy environment for new hair growth.

Incorporating Insights from Sun Protection Research

While sun protection for our faces and bodies are on our minds, it’s easy to overlook the hair and scalp. But solid research on sun protection for hair offers targeted advice. First, it emphasizes the importance of using antioxidant-rich products to counteract oxidative stress from UV exposure (plus this will help protect color treated hair); these include SPF for hair that forms a protective barrier against harmful rays. Regular deep conditioning treatments can restore moisture and strengthen the hair shaft, improving resilience against environmental stressors. By combining these protective strategies with an understanding of seasonal shedding, you can significantly reduce visible hair loss during summer.

When to Seek Professional Help?

Although summer shedding is generally harmless, it is important to recognize when professional help may be necessary. If you notice that shedding is excessive, persists beyond the typical seasonal period, or is accompanied by thinning patches, consult a dermatologist or trichologist. These specialists can perform diagnostic tests to rule out conditions such as alopecia, hormonal imbalances, or nutrient deficiencies. Early intervention can help manage underlying problems before they become severe.

The Takeaway

Summer hair loss is a common experience and is usually nothing to worry about. It reflects the body’s natural response to environmental and hormonal changes. By understanding the science behind seasonal shedding, you can take proactive steps to protect your hair during the warmer months. Paying attention to scalp health, using protective products, and maintaining good nutrition can help minimize shedding and keep your hair looking vibrant.

Summer shedding may seem like an inconvenience, but it is part of your hair’s natural rhythm. With proper care and the right preventive measures, you can enjoy the sunny season while ensuring your hair remains healthy and strong. Combining scientific knowledge with practical hair care strategies turns what might seem like a frustrating issue into an opportunity to improve your overall hair health.