May I have my hair washed and blow-dried at the hair-dresser on Monday (Rosh Chodesh Av). I have very thick, unrulely hair, that I can’t manage adequately. There will be no cutting, just wash and blow dry with additional straightening with an electric heating comb.
For Ashkenazim, washing hair is only permitted in the nine days (including Rosh Chodesh) in situations of extreme discomfort, or where washing is required as a form of medical treatment. I understand that without the hair-wash you would experience a great degree of discomfort, and therefore it would be permitted. However, you should ask the hair-dresser to use cold/lukewarm water rather than hot water, provided this is possible for the treatment involved. In addition, if you have the option you must have the treatment done on Sunday (before Rosh Chodesh) rather than during the nine days.
Sources: A number of poskim explain that under circumstances of great discomfort it is permitted to wash (in lukewarm water where possible). See Or Le’zion III, 27:5; Rivevos Efraim II, 154:4; Iggros Moshe, Even Ha’ezer IV, no. 84; Salmas Chaim IV, no. 219; Shevet Halevi VII, no. 127.