Which brings us to the question: how bad is heat for your hair?
While air drying is often perceived as the “healthier” option for hair, this really depends on the individual’s hair. Hair that air dries quickly may be in the clear. Yet hair that holds water for a long period of time, as well as repeated swelling and unswelling of hair fibers may cause some damage and breakage.
We found a study1 that tested different temperatures of heat to measure what level would cause a change in hair’s structure, and concluded that hair sees an irreversible change above 140C (or 284F.) Note that the average 1875 watt blow dryer reaches a temperature of 82C (180F.) In addition, this study found that blow drying hair 5 inches away from hair strands with constant movement was less damaging than air drying.
While there are more layers to this and there currently isn’t enough data to conclude one versus the other, we don’t think hair dryers or heat tools need to be feared, especially when used carefully and with heat protectants.
1. Bories MF, Martini MC, Et MF, Cotte J. (1984). Effects of heat treatment on hair structure. International Journal of Cosmetic Science, 6(5), 1467-2494