Many believe that stress or lack of sleep causes gray hair. The truth is that going gray is genetically encoded in our DNA. You're likely to follow in your parent's footsteps when it comes to how and when your hair will turn gray or white. The sun's rays can affect color producing pigment in a negative way.
Why We Go Gray
Hair color depends on pigment-producing cells (melanocytes) in the follicles beneath the scalp that produce melanin, the hair pigment. Melanin determines whether you are blonde, redhead or brunette, and its depletion over time causes the hair to lose color and become shades of white, silver and gray.
Effect of Sun on Hair
The sun has a tendency to lighten hair color. Because our hair is dead skin beyond the scalp, the active melanocytes in the hair follicle don't defend the hair shaft exposed to the sun. So the hair is forced to fend for itself, thereby becoming bleached and damaged.
Protection from the Sun's Rays
Melanin is nature's protection from the sun. The more melanin in your skin, the more natural protection you have from the sun's ultra-violet rays. The less melanin you have in your skin or hair, the less protection you have from the sun's harmful rays.
Sun Affects Melanocytes
The sun's rays can aggravate the melanocytes left in graying hair and cause them to become damaged and die, according to YogaHealthBenefits.com.
Sun Affects the Scalp
If graying hair coincides with thinning hair, the sun's UVA and UVB (aging and burning) rays can have serious effects on the scalp, since hair helps to protect the scalp by covering it. The scalp's overexposure to the sun without sufficient sun protection, like sunblock or a head cover, can lead to skin cancer.