Tip - Rash Under Arm in Toddlers | LIVESTRONG.COM

Your toddler has been playing all day, and now there's a mysterious rash under his arm. If a rash appears under your toddler's arm with no other symptoms, it could be from contact dermatitis, atopic eczema or even Lyme disease. Always consult your doctor for proper diagnosis and treatment if a rash is present on your toddler.