Rashes can appear in various areas of a baby’s body, each with distinct causes. Neck folds may trap milk, sweat, and moisture, leading to redness. Underarms and inner thighs often experience irritation due to friction and tight clothing. Small bumps may develop on the back and chest after sweating, especially if the baby is overdressed. The diaper area is susceptible to moisture and friction, while folds behind the knees and elbows can stay damp after bathing or sweating, requiring careful drying.