Hi, I Currently Have An Adult Case Of Hand-Foot-Mouth Disease

Hi,
I currently have an adult case of Hand-Foot-Mouth disease with the typical symptoms; sore throat, red itchy dots on my hands and feet. there are also a few red dots/sores that have appeared around the outside of my mouth on my face, and for some reason unknown to me, when they try to heal or scab over they have a yellow, hard, crystal-like substance form, kind of like a weird scab, on them. It doesn't hurt at all or cause me any inconvenience really, I was just curious as to what it is. I haven't been eating or staying hydrated the last few days as well as I should have (because my throat is pretty painful) but I don't know if that could be a factor for these yellow crystals or not. Do you know what it might be? thanks