The Prophet (peace be upon him) said: A man should not look at the private parts of another man, and a woman should not look at the private parts of another woman.
[Sunan of Abu Dawood, #4007, Narrated Abu Sa'id al-Khudri]
Masa'lah: It is permissible to arrange another person to remove under-arm hair. However, this is not permitted in the case of removing pubic hair. Nonetheless, this is allowed between those persons for whom gazing at each others private parts is permissible eg. husband and wife (although this is not commendable).