These diseases are often exacerbated by sun exposure. Some examples of autoimmune disease include Psoriasis and Lupus. It is important to evaluate these diseases to ensure that other organs are not involved. Infection of the skin can cause a rash as well. Bacteria, fungi, and viruses can all affect the skin.soriasis. Infection of the skin can cause a rash as well. Bacteria, fungi, and viruses can all affect the skin. Bacterial diseases generally appear as pustules, tender crusted areas, or in ring like patches (Lyme disease).