04 Common causes of skin rashes? 01. Allergies can occur due to the irritation caused by toiletries, creams, fabric detergent or softeners. The allergy can also be caused by food consumed or medicines. 02. Bacterial When bacteria enter open wounds it may result in rashes. The symptoms of scarlet fever and Lyme disease are perfect examples of rashes caused by bacteria. 03.Autoimmune Lupus, dermatomyositis and similar autoimmune diseases can cause skin rashes. 04. Viral Viral diseases such as measles, chickenpox and roseola cause rashes. These are often seen in children however it is not uncommon for adults to get them as well.