Skin, the largest organ of the body, is the body’s first defense against harmful microbes. Infections of the skin are very common and can be caused by viruses, bacteria, fungi, or parasites. The most common bacterial causes are Staphylococcus aureus and group A beta-hemolytic streptococci. The most common viral cause is Herpes simplex. And the most common fungi is Trichophyton rubrum.

Of resulting infections, impetigo, folliculitis, and boils are most common. Infections usually enter through breaks in the skin such as an insect bite. Other diseases such as measles, varicella, gonococcemia, travel through the system and only show on the skin secondarily.

Skin infections usually display locally as reddened and swollen skin and may form pus- or fluid-filled bumps. Some infection, however, may also only exhibit scaling without any other signs of inflammation.

Treatment typically involves thorough cleansing with an antimicrobial soap. Sometimes a compound that dries out the skin may help, such as aluminum chloride. Topical salicylates, which may help the skin to shed dead top-layer cells, may also help. Finally, topical antimicrobial agents can work on some infections.

Extensive, systemic disease often accompanied by fever and appearing on multiple parts of the body, will require systemic treatment.