Hello. So I am assuming that their profile states that they actually have reviews and are not new members of the site. They may have none as of yet.
If this is new for you as a host and you feel uncomfortable about anything when considering a guest, listen to that and ask them more questions. If you are still uncomfortable, decline the request in the nicest way possible.
I recently had a potential guest that was 20 and he wanted to book with a couple of his 19 y.o buddies. I have not had the best experiences when I have 3 boys staying, let alone very young ones that may be coming to party. Not only was he quite young (which can be a concern in terms of liability with alcohol or drug consumption issues here in Portland where pot is now legal), he was obviously inexperienced and wanted to rent for 5 days. I pointed out that he was new to the site with no prior reviews and asked if he could have someone provide a reference using Airbnb's reference feature...someone that would be qualified to speak to his responsible rental qualifications. If he would have been willing to make that happen, I would have taken this request more seriously as he would have been handling it as such. Alas I never heard from him again. I'm sure he didn't want to bother with taking the time to provide those assurances so who knows what else he wouldn't have bothered to tend to once he was here and had 5 days to run amok in my space. I feel like I diplomatically dodged a messy bullet.