Food on my face

Someone interrupts me while I'm eating to tell me I have food on my face. Why? I'm not the most fastidious of eaters (though not the messiest either), so if I'm eating something that is messy enough for me to get food on me, it's likely I'm going to get more on me. There's no point really in cleaning my face just then! After I've finished eating, then it's a good time.