Redness, swelling, heat and pain are usually caused by the following etiologies: 1. Redness, swelling, heat and pain is an infectious, specific reaction that occurs when bacteria, viruses, fungi or other pathogenic microorganisms, such as mycoplasma and chlamydia, infect the local tissue. Redness, swelling, heat and pain can also occur in skin allergies, such as skin excision of allergens or contact with pyrogenic sources, resulting in peripheral redness, swelling, heat and pain with dysfunction. 3. For example, redness, swelling, heat and pain around the joints may occur in common dermatomyositis or systemic lupus erythematosus, as well as in rheumatoid arthritis and rheumatoid arthritis.