Be Nice to Your Hair Tip #4: Avoid Heat

Treat your hair like a cashmere sweater.  Would you set your iron on high and iron the heck out of your cashmere?  Nope.  Well cashmere and hair are both made of keratin protein and both will be damaged by high heat.  Both will be damaged permanently.

Heat is bad for hair.  Avoid blow drying on high heat, curling irons, and the dreaded flat iron.  Heat damages the cuticle by causing bubbling, cracking, and chipping.  Heat also damages the hair's natural oils.  Heat can damage your hair's color (melanin).  In addition, heat damages the stretchy protein chains inside the hair's cortex.  This makes the hair more prone to breakage.  The heat can also cause the water inside your hair's cortex to boil and damage your hair from the inside out.
If you do choose to style with heat, use a heat protectant.  This helps, but doesn't completely protect the hair from heat damage.  Avoid heat protectants with a lot of alcohol in the formula.  How hot is too hot?  Above 150 degrees, the consequences of using heat become more severe.  However, all heat will cause some damage to your hair. Keeping the heat under 130 degrees is even safer.
 If you do blow dry, remove as much water as possible from the hair first.  Gently wrap your hair in a microfiber towel, a flower sack towel, or a 100% cotton t-shirt.   Don't use terry cloth.  Terry cloth towels damage the hair.  It also helps if you don't blow dry your hair completely dry.
Remember, if you are nice to your hair, it will be nice to you.

For more info, see these links:
Hair hot iron damage
How to protect your hair from heat damage
Thermal Protection:  Do they really work