Common skin infections include cellulitis, erysipelas, impetigo, folliculitis, furuncles and carbuncles. Cellulitis is an infection of the dermis and subcutaneous tissue that has poorly demarcated borders and is usually caused by Streptococcus or Staphylococcus species.
1. Cellulitis
Cellulitis is a painful, erythematous infection of the dermis and subcutaneous tissues that is characterized by warmth, edema, and advancing borders. Cellulitis commonly occurs near breaks in the skin, such as surgical wounds, trauma, tinea infections, or ulcerations, but occasionally presents in the skin that appears normal. Patients may have a fever and an elevated white blood cell count. Cellulitis can occur in any part of the body. Among the patients in the cohort above, the most common sites of cellulitis were the legs and digits, followed by the face, feet, hands, torso, neck, and buttocks.
2. Impetigo
Impetigo is most commonly seen in children aged two to five years and is classified as bullous or nonbullous. The nonbullous type predominates and presents with an erosion (sore), a cluster of erosions, or small vesicles or pustules that have an adherent or oozing honey-yellow crust. The predilection for the very young can be remembered by the common lay misnomer, “infant tigo.” Impetigo usually appears in areas where there is a break in the skin, such as a wound, herpes simplex infection, or maceration associated with angular cheilitis, but Staphylococcus aureus can directly invade the skin and cause a de novo infection.
3. Folliculitis
Hair follicles can become inflamed by physical injury, chemical irritation, or infection that leads to folliculitis. Classification is by the depth of involvement of the hair follicle. The most common form is superficial folliculitis which manifests as a tender or painless pustule that heals without scarring. The hair shaft will frequently be seen in the center of the pustule. Multiple or single lesions can appear on any skin-bearing hair including the head, neck, trunk, buttocks, and extremities. Associated systemic symptoms or fever rarely exist. S. aureus is the most likely pathogen; however, commensal organisms such as yeast and fungi occasionally appear, especially in immunocompromised patients. These lesions typically resolve spontaneously. Topical therapy with erythromycin, clindamycin, mupirocin, or benzoyl peroxide can be administered to accelerate the healing process.