The bottom line is that dirty hair does not grow faster than clean hair, so you might as well have a clean scalp and fresh hair. Your hair will look better, feel better, and be healthier as a result.
Wash to suit your needs and your hair type. Oily and fine or thin hair types should wash every one to two days. This schedule allows for removing buildup and the natural oils to stimulate hair health and growth. Wavy or curly hair and dry or damaged hair types should wash in the range of once every four to seven days.
“The speed at which hair grows is determined by genetics but there are other factors that can affect the growth rate. Age, diet, stress, hormonal fluctuations, scalp health, hair care practices, medications and other health conditions can potentially influence hair growth,” said master hair colorist, Stephanie Brown.
The slightly less short answer is that an oily scalp definitely contributes to hair loss but is often not the sole cause of it. Excess amounts of oils can trap and attract dirt, dandruff, and product build up, which clogs pores and prevents new hair growth.
People with oily hair or who use hair care products daily should consider washing their hair once every 1–2 days. People with dry hair can wash their hair less frequently. Those with textured or coily hair should only wash it once every 1–2 weeks.
On average, hair tends to grow between 0.5 and 1.7 centimeters per month. This is equivalent to around 0.2 to 0.7 inches. This estimate comes from The Trichological Society.
How long does hair grow in 2 weeks? On average, hair grows about half an inch per month. So, in two weeks, you can expect your hair to grow about one-quarter of an inch or half a centimetre every two weeks.
"The average individual can typically go 2 to 3 days without shampooing their hair. However, if your hair is visibly oily, you may not want to wait that long," she says. "Usually, you can go longer without washing your hair when your hair is styled up, but no one should ever go more than 14 days."
When to wash. Rossi generally tells his patients they should wash their hair once or twice per week. But if you've had chemical treatments that can make your hair drier — such as bleach, perms or relaxers — you might want to wash it less than once weekly to avoid breaking or brittle hair or split ends, he said.
If you normally wash everyday, it'll take time to get used to washing it less. So start by going an extra day or two in between your normal washes. Rinse your hair with water in between shampoos and try to build up to once a week. When your hair adjusts you'll notice a dramatic difference.
Not washing the hair regularly with shampoo has certain advantages like cost and time saving, reduced exposure to chemicals, and less risk of hair damage. However, it may increase the risk of scalp irritation and infections due to the buildup of sebum, dirt, and sweat.
Asian hair follicles are round, usually very straight, and strong. While not as dense as its counterparts, the hair is less likely to experience hair loss or breakage. Asian hair is also the fastest growing, at over half an inch per month.
After haircut
According to the American Society of Dermatology, after a hair cut in an average healthy person, it is usually a month to regrow your hair back by half an inch. If you are a female and lost inches of hair in a haircut, remember it takes almost a year to regrow about six inches of new hair.
Early on, any of the new hair growth you experience may just look like dark spots on your scalp, which can form as the new hair root grows from the follicle. These new hairs might be easier to see if you have dark hair and a light skin tone.
“Shampoo less and your hair will be more hydrated,” they said, which helps promote thickness. “Be sure to use sulfate-free products to preserve your hair's natural oils. (Their whole line of products is sulfate-free, should you be in the market.)
A healthy scalp should not have any redness or dryness and should be free of flakes or any signs of infection. Your scalp should look clean, smooth, and moisturized with no dryness on the surface. If you are experiencing any itchiness, irritation, or burning, this can indicate that your scalp is unhealthy.