People are “allowed” to do whatever they want within the limits of the law and that would apply to relationship choices too.
People are sometimes and somewhat influenced further (beyond legal limitations) by social mores and conventions.
Of course, what attracts someone to someone else is totally individual. It is not clear from current research how much of attraction is led by the frontal lobe. Thus, it is not clear how much control we have over being attracted to one person over another. Whether we follow through on the attraction is, I think, more in our control.
For myself, I have found that my initial views of someone as “attractive” to me often change radically as I get to know them.
Take the bald thread from the other day for example. In there, I confessed that as a general rule I am not attracted to men with hair loss. Is that shallow? You bet.
There have been exceptions to that in my life though. Men that I have come to know who have become very attractive to me because once I see their intelligence, sense of humor and kindness, I stop “seeing” their baldness.
I also knew in college a gorgeous man who shaved his head. My initial attraction to him faded as I came to know his egotistical, bullying ways.
I think, as kevbo wisely said, that when we make those shallow judgments, it is ourselves we are limiting.
Does this mean that out there somewhere is a sweet, sensitive, intelligent, funny man who elects not to bathe? Probably, but I won’t be dating him. That one I cannot overcome.