While both illnesses cause a rash, their patterns are distinct. Chickenpox (varicella) is known for its "dew drop on a rose petal" appearance, where red bumps quickly turn into clear, fluid-filled blisters that eventually crust over. Crucially, these lesions appear in waves, so you will see bumps, blisters, and scabs all on the body at the same time. The rash starts on the torso and face and can spread to cover the entire body, including the scalp and inside the mouth.
In contrast, Hand, Foot, and Mouth Disease (HFMD), usually caused by Coxsackievirus, has a very specific location pattern. The rash and blisters concentrate on the palms of the hands, soles of the feet, and in the mouth (often painful sores). The spots are often smaller and more uniform in their stage of development. A key differentiator is the presence of painful mouth ulcers in HFMD, which can be so severe that a child refuses to drink, posing a risk of dehydration. The rash on the limbs is typically not very itchy. By checking the location of the rash and looking for the mix of old and new blisters, a parent can often tell them apart with confidence.