What other infections cause rashes on skin and red bumps in face besides chicken pox. my son is 4?

Viruses, mostly.: Viral rashes are common in kids; chicken pox is the most popular, but just about any virus can cause a rash. Other possibilities include allergic reactions to medications or food additives, contact dermatitis, atopic dermatitis, and other things. It's impossible to make a precise diagnosis without seeing the rash, so you should consult a dermatologist, especially if your son is running a fever.

Many: There are many other illness that cause rashes. Most of them are viral. If your child still has the rash i would see your doctor.

Many causes: Red bumps may be due hives or possibly the beginning of impetigo.