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Treating skin infections in primary care

Maureen Benbow
MSc BA HERC RGN
Senior Lecturer
University of Chester

The skin or integumentary system is the most visible and yet most vulnerable organ of the body. It is complex, comprising skin, hair, nails and various multicellular exocrine glands and, because it is the largest and most visible organ, it is immediately apparent when something goes wrong. However, visible signs of other system dysfunction can be identified through changes in skin colour or sensitivity - for example, flushed skin, indicating pyrexia. The integument or skin accounts for 15-20% of a human's total bodyweight, weighs approximately 3kg and covers about 1.7 square metres. Approximately one-third of the total circulating blood volume is contained in the skin.(1) Skin is able to withstand a number of mechanical and chemical assaults and is capable of self-regeneration.(2)
Skin comprises two distinct layers: the surface layer, called the epidermis, and the inner dermis. The epidermis is constantly being replaced by dead cells from its lower layers but retains its waterproof properties through the presence of keratin and production of lipid by the Odland bodies. When intact, skin forms a dry, impermeable and efficient barrier to pathogens; however, keratin is capable of absorbing large quantities of water, which may lead to maceration (a softening or sogginess of the tissue owing to retention of excessive moisture(3) and skin breakdown.(4) The slightly acidic pH of skin helps to reduce the pathogenic bacteria, and encourages and protects commensal bacteria and fungi, which contribute to normal skin function. The Langerhans cells, a type of tissue macrophage, are antigen-presenting cells that ingest and digest bacteria and other substances and are found in the epidermis. Mast cells, which contain histamine, comprise the skin's immune system.(5) Any breach in the skin extending to this level exposes the body to infection.
The thickest layer, the dermis (2-5mm) is composed of dense fibrous connective tissue and contains numerous collagenous and elastic fibres surrounded by a gel-like substance.(2,5) This structure makes the dermis strong and stretchable. The capillary network lies directly under the basement membrane to supply oxygen and nutrients to the overlying epidermal cells. Collagen is the body's main structural protein that gives skin its tensile strength and acts as a buffer to external pressure; elastin provides the property of elastic recoil.(2) Accessory structures such as hair follicles, sebaceous glands, sweat glands, nervous tissue and some muscle tissue are also present. Nerves called sensory receptors detect pain, temperature, pressure and touch.(6)
Macrophages and fibroblasts, key cells for healing, are found in the gelatinous fluid matrix of the dermis.

Infection
Anyone with a break in the skin is at risk of infection. The types and severity of skin infections can vary even in a person without health complications; however, certain conditions or diseases can put a person at greater risk for infection. These include diabetes, which causes reduced blood flow to the skin; AIDS (immunosuppression); chronic cardiac and respiratory conditions, which reduce the oxygen-carrying capacity of the blood; and inflammatory skin conditions, such as psoriasis and eczema. Skin infections may arise from both internal and external routes, with external being more common. The more common infections are:

  • Bacterial - mainly caused by either Staphylococcus aureus or Streptococcus pyogenes and present as impetigo, folliculitis, abcesses and furuncles or cellulitis.
  • Viral - caused by papova, pox or herpes and present as human papillomavirus, the molluscum contagiosum virus or herpes simplex virus.
  • Fungal - dermatophytes presenting as athlete's foot, candidiasis or sporotrichosis.

Bacterial infections
S aureus can penetrate via a breach in the skin, hair follicle or nail fold; the first resulting in impetigo, the second in folliculitis or furuncle where pus forms as part of the inflammatory response, and the third in paronychia or whitlow.

Impetigo
Impetigo is a superficial, contagious skin infection of the epidermis and/or dermis occurring mostly on children's faces, which presents as pustules that quickly break to form crusts or blisters (bullous impetigo). In most cases there is little or no pain, no localised erythema or systemic manifestations. On confirmation of diagnosis by a Gram stain, the treatment will comprise systemic antibiotics as opposed to local antibiotic therapy, to reduce the risk of resistance.(7) Measures should be taken to reduce the risk of cross-contamination - for example, handwashing and not sharing towels.

Folliculitis
Folliculitis is infection of hair follicles (see Figure 1); pus may be present in red, irritated hair follicles; and there may be evidence of hair damage. Boils are tender, swollen areas with pus in the centre, which form around hair follicles, often on the neck, breasts, buttocks and face, and there may be a whitish, bloody discharge. Carbuncles are clusters of boils with the previous signs but with generalised symptoms of lethargy and fever. Paronychiae and whitlows occur around the nail and, in common with the previous conditions, show the classic signs of inflammation - heat, erythema, swelling and pain. Treatment focuses on keeping the skin clean, and systemic antibiotics and warm soaks regularly applied may ease discomfort.(8)

[[NIP27_fig1_35]]

Cellulitis
Group A streptococci is usually inoculated into previously damaged skin (scratches, human or insect bites or injuries that occur in water) where infection is established, cellulitis or erysipelas may result. Cellulitis is a spreading skin infection that is characterised by a diffuse inflammation of connective tissue. Cellulitis commonly affects the legs in adults following a minor injury or interdigital infection.
Symptoms include swelling, tenderness, localised heat, bruising, blisters, leaking exudate, fever and headache. Predisposing factors to cellulitis include a previous history of cellulitis; venous insufficiency; chronic independent oedema and lymphoedema (swelling due to obstruction of lymphatic channels); damaged lymphatic system (eg, postsaphenous venectomy for coronary artery bypass grafting, postmastectomy); obesity; immunosuppression, including malignancy, HIV/AIDS and corticosteroid use; intravenous drug misuse; and possibly diabetes mellitus and alcohol misuse.(9) Complications may include septicaemia, abscess formation, meningitis, necrotising fasciitis or endocarditis. Diagnosis is based on clinical signs and laboratory identification of the infecting organism. Treatment will be determined by signs, symptoms and prognosis, and will generally comprise systemic antibiotics, leg elevation and dressings to cope with the exudate and relieve associated pain.(10)

Staphylococcal scalded skin syndrome
Staphylococcal scalded skin syndrome is characterised by peeling skin (see Figure 2). The disease mostly affects infants, young children, and persons with a depressed immune system. The most common symptoms of staphylococcal scalded skin syndrome include a crusted infection site, often on the nose or ears, red, painful areas around the infection site, blistering, fever, chills, weakness, dehydration and extensive exfoliation. Diagnosis is usually confirmed by biopsy.

[[NIP27_fig2_36]]
 
Patients will normally be hospitalised, often in a burns unit, with treatment comprising general support measures, intravenous antibiotics, wound and skin management (antiseptic washes).(11)

[[NIP27_box1_37]]
 
Fungal infections
Fungal infections of the skin are common between the toes (athlete's foot), in the groin, skin folds, vagina, penis,corners of the mouth, nail beds and under the breasts. Candidiasis (a yeast) causes infection in warm moist areas of the body, particularly in immunocompromised people. Antibiotics kill off normal body bacteria, allowing the yeast to grow unhampered.
Symptoms depend on the location but may include itching or burning, swelling, cracking, rash, patches that ooze white fluid, or pimples. Fungal infections are commonly seen in people with diabetes, obesity, inflammatory skin conditions, vascular insufficiency, on steroids, the immunosuppressed and those living in tropical environments. Diagnosis is usually based on clinical signs and possibly scrapings if there is doubt. Antifungal therapy is recommended, but investigation of the underlying cause should be a priority in cases of repeated infections, as well as advice on good hygiene.(12) Other fungal infections include ringworm of the skin, nail bed, groin and scalp and are treated with suitable antifungal preparations and good hygiene to prevent recurrence and transmission to others.

Viral infections
Viral infections such as those caused by the herpes simplex or zoster virus, such as cold sores or shingles, may lie dormant for long periods and are associated with environmental changes and an impaired immune system. Symptoms may be generalised or local depending on the severity and transmitted via direct contact. Analgesics, nonsteroidal anti-inflammatory medications and local anaesthetic may relieve symptoms, but most conditions are self-limiting. There is no strong evidence for the use of antiviral therapy of efficacy in reducing pain or other symptoms in immunocompetent people, and it should be reserved for severe cases.(13) Where possible, the known trigger factors should be avoided to prevent recurrence.
Warts are noncancerous skin growths, more common in children, caused by the papillomavirus. Warts can spread to other parts of the body and from person to person by direct contact. There are many different types and sizes of warts as there are approximately 60 papillomavirus types. A policy of nontreatment is advocated as they often resolve spontaneously within two years unless they are painful, in which case individuals should be referred for a professional opinion (eg, to a podiatrist) rather than apply over-the-counter treatments.(14)

Conclusion
It has only been possible here to briefly review a small number of skin infections. For definitive information and advice on best practice in management, readers should access the Prodigy guidance website.

References

  1. Herlihy B, Maebius N. The human body in health and illness. London: WB Saunders Company; 2000.
  2. Wysocki AB. Anatomy and physiology of skin and soft tissue. In: Bryant R, editor. Acute and chronic wounds. Nursing management. London: Mosby; 2000;1:1-16.
  3. Cutting K. Definition of terms. Journal of Wound Care Resource File. London: Macmillan Magazines; 1996.
  4. Lloyd N, Moody M. Skincare for incontinent patients. Nursing and Residential Care 1999;1:9;15-7.
  5. Tortora GJ, Anagnostakos NP. Principles of anatomy and physiology. 5th ed. London: Harper & Row; 1993.
  6. Martini FH, Bartholomew EF. Essentials of anatomy and physiology. 2nd ed. New Jersey: Prentice Hall; 2000.
  7. Prodigy. Impetigo. Available from http://www.prodigy.nhs.uk/guidance.asp?gt=Impetigo
  8. Prodigy. Fungal infections. Available from http://www.prodigy.nhs.uk/guidance.asp?gt=Fungal%20 (dermatophy te)%20infections%20 —%20skin%20and%20nails
  9. Prodigy. Cellulitis. Available from http://www.prodigy.nhs.uk/guidance.asp?gt=Cellulitis
  10. Benbow M. Swollen leaking legs. Nurse2Nurse 2002;2:8;34-8.
  11. University of Maryland Medical Centre. Dermatology. Available from http://www.umm.edu/dermatology-info/staph.htm
  12. Prodigy. Candidiasis. Available from http://www.prodigy.nhs.uk/guidance.asp?gt=Candida%20%97%20skin%20and%20n...
  13. Worrall G. Herpes labialis. Clin Evid 2004;11:2174-81.
  14. Prodigy. Warts and verrucae. Available from http://www.prodigy.nhs.uk/guidance.asp?gt=Warts%20and%20verrucae

Resources
Prodigy Guidance
W:www.prodigy.nhs.uk/guidance.asp

Skin Care Campaign
For details on skin information days
W:www.skincare campaign.org

Tissue Viability Society
To book a free Tissue Viability Society study day in your
organisation
E:tvs@dial.pipex.com.
E:Maureen. Benbow@btinternet.com