There are more reasons for the sudden appearance of hives in eight-month-old babies, which may be related to allergies, cold, sun exposure, mosquito bites and other reasons. 1. Cold urticaria: babies are prone to urticaria when stimulated by cold. Such as contact with cold air or cold water, the contact area will appear angioedema, air masses, corn-like protrusions and other symptoms. 2. Solar urticaria: When the baby is exposed to sunlight or ultraviolet radiation, the local skin will appear mucous membrane small blood vessels temporarily dilated, showing symptoms such as erythema, itching, and wheals. 3. Allergic urticaria: clinically this type is more common, may be associated with the baby’s contact with allergic foods, or objects. For example, some parents add crab meat porridge, if the baby is allergic to crab meat, hives may occur. Some parents used to give the baby to wear gold and silver jewelry, may also lead to contact with the skin, hives. 4. Mosquito bites: mosquito bites can appear pimple urticaria, often manifested as red prominent skin surface, erythema. If the baby has a rash, parents are advised to take the child to the hospital in a timely manner, improve the examination such as blood test, allergen test, etc., with the help of the doctor to clarify the cause, and actively cooperate with the doctor to deal with or treatment.