According to the Centers for Disease Control and Prevention, true influenza can cause a fever with a rash but usually only in children. Health Central states that, even though influenza rarely causes a skin rash in adults, it isn't impossible for it to happen, especially if the person has a history of skin rashes caused by allergies.
Health Central also sites other diseases that cause rashes in adults that may produce symptoms similar to those of influenza. Shingles, caused by the chicken pox virus, starts with an extremely painful rash on the face and body and may include flu-like aches and pains. Rocky Mountain spotted fever, spread by tick bites, starts off feeling like the flu with a rash on the extremities appearing on the fourth day, spreading from the feet to the hands and then to the rest of the body. Lyme disease, another illness spread by ticks, may also present with a rash as the disease progresses. Meningitis starts off with a fever, headache and a stiff neck, possibly with a rash, that can develop into a potentially lethal fever. Mononucleosis, lupus, fifth disease and roseola are other examples of illnesses that produce a rash and flu-like symptoms.