It could be something as simple as he just bumped into something and scraped his skin. It could be a skin allergy, a flea or parasite allergy. If it doesn't appear to get better, you might want your vet to take a scraping.
She could have mites, or mange which is usually noticable first near the face. The best thing to do is to speak to a vet about this, especially if you do not notice any scratching or rubbing.
If there is no swelling, discharge, or areas that looked scratched it is not a emergency. You should make a appointment to see your vet as soon as possible.
