Skin Infections

Skin infections can be caused by viruses, bacteria, or fungi. Viruses of the human papilloma virus family cause warts which can appear on any part of the body but commonly affect the hands. On the sole of the foot the infection produces a verruca, which is a wart pushed into the skin by the pressure of weight bearing. While these may disappear spontaneously, they may be present for many years. There is no treatment other than destruction using either topical agents such as salicylic acid or some form of surgery. Genital warts are a sexually transmitted disease which may, in the female, predispose to the development of cervical cancer. Herpes simplex viruses cause recurrent cold sores, painful ulceration and inflammation of the mouth and gums (called gingivostomatitis) and genital herpes. The virus lives in part of the spinal cord called the dorsal root ganglion roughly corresponding to the part of the skin that the virus first entered (so if you kiss someone with a cold sore you're likely to develop one on your lips; if you have unprotected sex with a sufferer of genital herpes you're likely to get genital herpes). Attacks occur as a result of the depression of the immune system - commonly caused by sunlight, illness causing fever or stress and anxiety. There is often itching, burning or pricking before the blisters, followed by ulcers, develop and prompt treatment with anti-viral agents may reduce the severity of the attack. Viruses of the poxvirus family cause the development of small pearly swellings, called molluscum contagiosum (because they look like shellfish and are very contagious) - more commonly affecting children but occasionally seen in young adults. There is no treatment and they should resolve spontaneously. Herpes zoster infection causes chickenpox, with widespread blisters lasting up to 10 days or, more commonly in the adult, shingles.

Bacterial infection of the skin produces impetigo, which is a superficial infection producing golden coloured blisters or crusts due to the bacterium Staphylococcus aureus. This is usually a disease of childhood, and often start around the nose and mouth, but it is highly infectious and can spread to other close contacts (including the parents) antibiotic treatment is required. The bacterium streptococcus is responsible for the disease erysipelas, more painful than impetigo and usually affecting the face or the lower leg, producing an angry red rash with a well-defined edge. There may be associated fever and systemic upset. Treatment is by antibiotics. Some patients suffer recurrent attacks, which can progress very swiftly - it may help if they have access to a stock of antibiotics. Cellulitis is a deeper infection of the skin and subcutaneous tissues, sometimes following injury whether protective barrier of the skin has been breached - by a scratch or a bite for example. There is swelling of the affected part together with pain and overlying redness: besides treatment to reduce pain and inflammation antibiotics will be required.

Fungal skin infections most commonly involve agents called dermatophytes which cause ringworm, or tinea, which also infect animals, which is where we often catch them from. While any part the body may be affected, tinea pedis, or athlete’s foot, is the most usual site. If it affects the scalp (causing hair loss) it’s tinea capitis, while in the groin it’s tinea cruris. These germs are all moulds, and they produce enzymes which dissolve protein and so allow invasion of the skin. They cause a scaly rash which may spread outwards and leave a clear centre (which is why it's called ringworm). It can be intensely itchy. There are effective treatments, but reinfection, particularly in sports people, is a frequent occurrence. Yeasts which infect the skin include Candida albicans, and mallasazia furfur. Candida albicans often affects moist places like the mouth and the vagina, and can cause a chronic infection of the nail fold. Mallasazia furfur affects the trunk producing red brown patches which scale and often become de pigmented - called Pityriasis Versicolor. Persistent or repeated infections by Candida may be a presenting feature of diabetes mellitus. Yeast infection may be treated by topical treatments or oral agents.
 
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