When considering Air Drying vs. Blow Drying, it’s possible to jump to the wrong conclusion as to which causes the most damage. It might seem counterintuitive, yet scientific research suggests that air drying can actually be more damaging to the internal structure of the hair than blow drying. However, this only holds true when the blow dryer is used properly. Let us explain in more detail.
Blow drying can cause more surface damage (to the cuticle), especially when the heat setting is too high or the dryer is held too close to the hair. The intense heat can strip away moisture from the outer layer, making the hair shaft rough and prone to split ends and breakage. Over time, this surface damage can accumulate, leading to dullness and a loss of natural shine. However, if the blow dryer is used correctly—at a low or medium temperature, with the dryer kept at least 6 inches away from the hair, and always in motion—the risk of cuticle damage is significantly reduced.
In contrast, air drying generally enables the surface of the hair to remain smoother and less disturbed, which may help maintain a shinier and softer appearance. That said, air drying is not without its drawbacks: while the cuticle remains relatively intact, the hair shaft swells as the cortex absorbs water and remains swollen for longer periods. This puts prolonged pressure on the delicate proteins, such as keratin and the cell membrane complex, that are essential for hair strength. Repeated cycles of swelling and shrinking, known as hygral fatigue, can ultimately weaken the internal structure of the hair, making it more susceptible to breakage, frizz, and loss of elasticity.
Regarding scalp health, another potential detriment of air drying is that it can sometimes encourage fungal growth, particularly of the Malassezia species. This type of fungus thrives in moist environments, and letting the scalp remain damp for extended periods creates a perfect condition for it to multiply. An overgrowth of Malassezia can contribute to common scalp issues such as dandruff, itching, and irritation, potentially disrupting the natural balance of the scalp microbiome. In contrast, blow drying, when used wisely, helps evaporate moisture more quickly from the scalp, making it less hospitable to fungal growth and supporting a healthier scalp environment overall.
All in all, best practice recommends using your hair dryer on a low to medium setting, keeping the dryer at a 6-inch distance from the hair, and always moving it around to prevent heat concentration. Additionally, applying a heat protectant product can act as a safeguard for both the cuticle and the internal proteins. Generally, air drying may still be considered a good option for short periods of time or for individuals with very fine or fragile hair, as it minimizes exposure to heat. Ultimately, the healthiest approach may involve combining both methods to take advantage of their respective benefits while minimizing risks to both hair and scalp.
The Science Behind “The Swelling Effect”
When hair is wet, the cortex (the inner layer) absorbs water and swells. Because hair dries slowly during air drying, the complex proteins are kept in a swollen state for an extended period. This repeated process of swelling and de-swelling is known as hygral fatigue, which can lead to permanent structural damage and loss of elasticity, making hair appear frizzy and brittle.
The Annals of Dermatology published a landmark study in 2011 titled “Hair Shaft Damage from Heat and Drying Time of Hair”. This study compared the two different hair drying methods. Here’s an excerpt: “The hair shaft swelled when it was wet… and the cell membrane complex (CMC) was damaged only in the naturally dried group… although the hair surface showed more damage with increasing temperature, using a hair dryer at a distance of 15 cm (approximately 6 inches) with continuous motion caused less damage than drying hair naturally.”
Research conducted by The Journal of Cosmetic Science has indicated other weaknesses of air drying. It’s often been highlighted that CMC (recognized as the “glue” which holds hair cells together) is particularly vulnerable to staying wet for a longer period of time. “Prolonged exposure to water causes the hair fiber to swell and puts pressure on the delicate cell membrane complex.”
The “Hybrid” Recommendation
To minimize damage to both the surface and the core, most experts recommend a hybrid approach:
- Air dry your hair until it is about 70–80% dry.
- Blow dry the remaining 20–30% on a low or medium heat setting, keeping the dryer moving and at least 6 inches away from the hair. Always use a heat protectant product, which acts as a physical barrier for the cuticle.
Enjoy Your Hair!!
Mickey