Acute paronychia is a very painful and tender infection of the proximal and lateral nail folds. It is usually caused by Staphylococcus aureus; occasionally, group A streptococci, and gram-negative bacteria are responsible. The nail folds become red and swollen, and there may be frank drainage of pus (Fig. 73-1). After several months, the nail may break (onycholysis) or become ridged. Acute paronychia frequently occurs in diabetics and in patients who are immunocompromised.

Chronic paronychia has a less dramatic presentation and is often due to Candida albicans. Contact dermatitis, fixed drug eruptions, psoriasis, and dyshidrotic eczema also cause chronic paronychia. Repeated hand trauma or washing leads to a loss of the seal between the nail plate and nail folds, and infectious or irritative agents can gain entry. Dentists, bakers, and construction workers are often affected.