Does my appearance hinder my ability to get a job?

I've been job hunting for something a little bit above minimum well alot i guess but alot of places i apply to require me to be b4 a customer or so. Im 19 but alot of people continue to tell me i look like im 15-16 and I often get odd looks when i apply to these places. Do they want an apparently older looking male to represent the and if so what should i do? Are there any other decent jobs out there that anyone one can mention? I dont want a fastfood job or minimum wage... I thought my youthful appearance was a plus *sigh*