Most rashes appear in one localized area on the skin, but one rash moves from place to place on the body. Known as hives, or urticaria, this moving rash is generally harmless in babies. However, only a doctor can diagnose the rash and determine the underlying cause and appropriate treatment.
Hives appear as itchy red welts that "move" around the body. Hives pop up in one place on the body and then disappear, and reappear on a different location of the body a few hours later. Some hives appear as small individual spots, while others cluster together to form large connected bumps as big as dinner plates. The rash may last for just a few hours or up to a week.
An allergic reaction is the most likely culprit of hives, especially if you've introduced a new food in your baby's diet. Generally, hives appear immediately after giving the new food, but if you've introduced milk, the hives and accompanying symptoms often do not appear until seven to 10 days later. An allergic reaction might also occur if your baby met a new animal, had an insect bite or started a new medication. Physical stimuli, such as exposure to pressure, cold and sun, as well as scratching and sucking, sometimes cause hives. Infections and contact with chemicals also can cause hives. In some cases, the cause is unknown.
To treat your baby's rash, talk to your doctor to determine the possible cause. Often, mild hives disappear without treatment. If the doctor determines the trigger, the doctor might prescribe a medication, or recommend an antihistamine suitable for a baby. Do not give any medication without your doctor's consent. If you've recently given a new medication, used a different soap or introduced a new food, stop using those items and see if the hives disappear and stay gone. Use products free of chemicals, dyes and odors.
Hives is the only true moving rash that travels from one place to the other on the body during an outbreak, but other rashes may come and go. If you over-bundle your baby, heat rash is a possibly. Characterized by tiny, prickly clear or red spots, heat rash generally goes away without treatment when the baby feels cooler. It can reappear when the baby becomes too warm. Dress your baby in lightweight clothing to prevent heat rash.
Patches of red, scaly and itchy skin called eczema also pop up from stimuli, such as irritating substances and extreme temperatures. When your baby's no longer exposed to the irritating stimulus, the eczema may subside but reappear at another time and at another place on the body. Avoid possible irritants and bathe your baby only every third day to treat eczema. Gently pat dry the skin, and cover the skin in an unscented moisturizing cream or ointment, as recommended by your doctor.