Ann Dermatol.  2011 Nov;23(4):455-462.

Hair Shaft Damage from Heat and Drying Time of Hair Dryer

• Lee Y
• Kim YD
• Hyun HJ
• Pi LQ
• Jin X
• Lee WS

Abstract

BACKGROUND
Hair dryers are commonly used and can cause hair damage such as roughness, dryness and loss of hair color. It is important to understand the best way to dry hair without causing damage.
OBJECTIVE
The study assessed changes in the ultra-structure, morphology, moisture content, and color of hair after repeated shampooing and drying with a hair dryer at a range of temperatures.
METHODS
A standardized drying time was used to completely dry each hair tress, and each tress was treated a total of 30 times. Air flow was set on the hair dryer. The tresses were divided into the following five test groups: (a) no treatment, (b) drying without using a hair dryer (room temperature, 20degrees C), (c) drying with a hair dryer for 60 seconds at a distance of 15 cm (47degrees C), (d) drying with a hair dryer for 30 seconds at a distance of 10 cm (61degrees C), (e) drying with a hair dryer for 15 seconds at a distance of 5 cm (95degrees C). Scanning and transmission electron microscopy (TEM) and lipid TEM were performed. Water content was analyzed by a halogen moisture analyzer and hair color was measured with a spectrophotometer.
RESULTS
Hair surfaces tended to become more damaged as the temperature increased. No cortex damage was ever noted, suggesting that the surface of hair might play a role as a barrier to prevent cortex damage. Cell membrane complex was damaged only in the naturally dried group without hair dryer. Moisture content decreased in all treated groups compared to the untreated control group. However, the differences in moisture content among the groups were not statistically significant. Drying under the ambient and 95degrees C conditions appeared to change hair color, especially into lightness, after just 10 treatments.
CONCLUSION
Although using a hair dryer causes more surface damage than natural drying, using a hair dryer at a distance of 15 cm with continuous motion causes less damage than drying hair naturally.

Keyword

Hair damage; Hair dryer; Heat; Natural ambient dry

MeSH Terms

Cell Membrane
Hair
Hair Color
Hot Temperature
Light
Microscopy, Electron, Transmission
Water
Water

Figure

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  Fig. 1 Illustration of transpiration moisture.

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  Fig. 2 Hair surface damage measured by scanning electron microscopy after the hair drying process. The extent of damage to hair surfaces increased as the temperature rose. Treatments: (A) no treatment, (B) shampooing and drying without using a hair dryer (room temperature, 20℃), (C) shampooing and drying with a hair dryer for 60 seconds at a distance of 15 cm (47℃), (D) shampooing and drying with a hair dryer for 30 seconds at a distance of 10 cm (61℃), (E) shampooing and drying with a hair dryer for 15 seconds at a distance of 5 cm (95℃).

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  Fig. 3 Cuticle layer damage measured by transmission electron microscopy after the hair drying process. The outer-most cuticle layer is damaged only during the 95℃ drying process. Treatments were as described in Fig. 1.

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  Fig. 4 Cortex layer measured by transmission electron microscopy after the hair drying process. In all conditions, there were no signs of damage. Treatments were as described in Fig. 1.

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  Fig. 5 Cell membrance complex (CMC) damage measured by lipid transmission electron microscopy after the hair drying process. Only the naturally dried group showed bulging of the CMC layer. Treatments were as described in Fig. 1. The arrowhead indicates bulging portions in the intercellular lipid layers.

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  Fig. 6 Results of moisture content analysis. Treated groups had lower moisture contents than the untreated group, which were not statistically significant.

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