Everything you need to know about common rashes in kids, like eczema, roseola, diaper rash and more. Whether it's pink pimples on a newborn's cheeks or fire-engine-red welts on a feverish toddler, a child's first rash can alarm even the most zen of parents. But bumps and blotches are simply our skin's way of reacting to certain irritants, infections or hormonal changes, and generally are not a cause for alarm.