Sun & Hair Growth Rate

Blond woman spending time in the sun
Photo: Zapylaiev Kostiantyn/Shutterstock
Q: Does the sun make your hair grow faster? Is spending a lot of time outside in the sun good or bad for hair growth?
 
A: Contrary to what some people might hope, spending time in the sunshine does not make your hair grow faster. Your hair follicles operate according to their own biological cycle, with hair growth influenced by factors inside your body such as your genes, hormones, nutrition, age, and overall health. Plants use sunlight to create energy through photosynthesis, but human hair does not use solar light to boost its growth rate.
 
Hair growth occurs under your skin inside the scalp's hair follicles. On average, human head hair grows about 1.2 centimeter (roughly 0.5 inches) each month, though exact speeds differ from person to person. Some people report perceived faster growth in the summer, but this minor seasonal shift is usually caused by better blood circulation from warmth, temperature changes, and higher Vitamin D levels throughout the body. UV exposure itself does not increase the growth rate.
 
However, sun exposure does have significant effects on your existing hair shaft and scalp health, and excessive ultraviolet (UV) exposure (including both UVA and UVB rays) can cause damage:
 
• Damage to the Hair Shaft: Hair is mostly made of a protein called keratin. UVB rays break down disulfide bonds and amino acids within the hair shaft, while UVA rays damage the outer cuticle. Spending long periods in the sun leaves hair weaker, drier, rougher, more porous, and more likely to split and break.
 
• Fading and Color Changes: Sunlight breaks down melanin, which is the natural pigment that gives your hair its color. While this creates natural highlights, this color change is a sign of sun damage. Because the visible hair shaft is made of dead, keratinized tissue, it cannot self-repair this damage.
 
• Scalp Sunburn and Extra Hair Loss: The scalp is prone to sunburn, especially along part lines or areas with thinning hair. Sunburn triggers localized inflammation, oxidative stress, and tissue irritation. While a simple sunburn rarely causes permanent baldness, acute scalp inflammation from severe UV exposure can trigger telogen effluvium. This is a temporary form of excess hair shedding that often appears 2 to 3 months after the initial sun damage.
 
• Who Is Most at Risk: People with fine, light, or chemically treated hair (such as bleached or dyed hair) are especially susceptible. Light hair contains less protective melanin, while chemical treatments already weaken the protective protein layer, making the hair twice as vulnerable to UV breakdown.
 
Woman wearing a straw hat to protect her hair from the sun
 
So, while spending time in the sunshine doesn't directly speed up hair growth, excessive UV exposure can compromise your hair's strength and disrupt healthy scalp conditions.
 
To keep your hair and scalp in great shape while enjoying the outdoors, take simple protective measures: wear a hat that blocks UV rays, use sunscreen designed for the scalp and hair, stay in the shade during peak sun hours, and wash out chlorine or saltwater right after swimming.
 
©Hairfinder.com
 
See also:
 
How hair responds to sun exposure
 
Is there something like sun block for hair?
 
Does the tanning bed hurt your hair in any way?