Hair is most vulnerable to damage when it is wet.
The results documented in the published paper referenced above show that letting hair dry naturally causes the cortex (the thickest layer of hair) to swell and become weaker, as the swelling puts pressure on the delicate proteins that hold hair together.
The best way to dry your hair is to let it air dry under the fan as much as possible. However, some experts believe combining air and blow-drying is healthier than just air drying. It is good to let your hair air-dry seventy percent of the way and then blow-dry till they become dry ultimately.
While excessive heat can cause damage to the surface layer of the hair, air-drying can cause trauma to that inner lipid layer, which will make your strands weaker as a result. Over time, something called hygral fatigue happens, i.e. repeated swelling of the hair.
It turns out letting your hair air dry after you've washed it is causing more damage than you think. According to Dr Tim Moore (the Australian Vice President of Smart Devices) leaving your hair wet for extended periods of time is putting excessive pressure on your strands resulting in split ends.
When used timely and moderately, blow drying is better for scalp and hair. Air drying (like over washing) over an extended period can cause scalp to compensate, over produce oil leaving hair more oily, and causing you to fight the imbalance with more and more shampoo for oily scalp and hair.
For example, cold and dry air can actually cause the cuticle of the hair strand to lift ever so slightly. As a result, moisture doesn't stand a chance of staying locked into the hair shaft. This explains why many women find themselves battling breakage and frustrating frizz during this frigid time of year.
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.
You want to gradually dry your hair instead of sucking out every bit of moisture. Always keep your hairdryer six inches away from your scalp and keep moving it around for the best results. Or you could add a diffuser attachment to your hairdryer as it spreads out the heat and creates an even air stream.
Heat is damaging to hair, so blow drying with cold air is a healthier choice for your mane. It would take a long time to dry and style damp hair using only cold air, but cold air is great for touching up dry hair or setting a heat style.
Hair is at its most fragile when wet, so if you go to bed with it damp and proceed to toss and turn against a pillow, you run a higher risk of breakage. But aside from being rough on your delicate strands, hitting the pillow with damp hair puts you at risk of developing skin infections, primarily on your scalp.
Celebrity hairstylist Bridget Brager adds that while blow drying your hair with hot hair may be faster, the heat can be damaging, and using cold air is actually healthier. "Styling hair at a lower temperature is imperative to maintain hair health," she says.
Use a soft towel to pat or blot your hair dry. Work to squeeze water from the hair without being rough with your strands. Drying your hair in separate sections also helps. This tip is ideal when learning how to dry long hair without heat.
“What tends to happen, particularly in humid weather, is that the cuticles don't seal properly, which leads to frizz.
Towel-drying your hair is important to help remove water, so hair can dry faster. Yet, the wrong technique can result in extra frizz, tangles, and poufiness. The right ways to air dry hair include gentle drying techniques. It's best to use your towel to squeeze water out from your hair.
Every once in a while, it's OK to wear your hair tightly pulled back, but you want to avoid wearing a tightly pulled hairstyle every day. The constant pulling can cause strands of your hair to break or fall out. In time, the continuous pulling can damage your hair follicles.
However, if you would like to leave your hair straight, push it all up in one uniform direction and let it dry naturally. This also ensures that you won't get any random waves or kinks from your head resting against the pillowcase,” she adds.
After leaving the shower, start by dabbing off excess water with a microfibre cloth. Avoid rubbing the hair vigorously, as the friction causes the strands to tangle and generate frizz. Then, keep your hair wrapped for 10 to 15 minutes.
Air dry hair
If you have the time, it's best to let your hair air dry naturally. Air drying minimizes heat damage and allows your hair to rejuvenate at its own pace.
A lot of people need around 40 minutes for their hair to dry naturally.. I need 40 min for diffusing (blow drying). We all have different air drying times. You could try airdrying under the sun or stand next to a heating device or dehumidifier to decrease drying time.