Urgent warning: If you have fever, rapidly spreading rash, severe pain, pus or discharge, breathing difficulty or fainting, seek emergency care immediately. Itching, redness and small bumps under the chest and on the back may be due to several causes (sweating and friction, folliculitis, intertrigo or fungal overgrowth in skin folds, contact dermatitis or small inflammatory lesions). This page provides guidance only and not a medical diagnosis or treatment. General low‑risk home measures: keep the area clean and dry; shower after heavy sweating and dry the skin gently; choose loose, breathable clothing (e.g., cotton) and avoid tight synthetic garments; stop any recently started detergents or scented products and monitor for change; photograph the lesions to follow any progression. If the condition worsens, spreads, or produces foul‑smelling discharge, consult a healthcare professional. When to see a doctor: If there is no clear improvement within a week or two, symptoms worsen, or pain/pus/fever develop, see Family Medicine or Dermatology and Venereal Diseases. Infectious Diseases and Clinical Microbiology consultation may be needed for suspected widespread or difficult infections. Take note of onset, new products used, recent sweating or activities, current medications and photos for your visit. This is general guidance. For definitive assessment, testing or treatment, be seen in a healthcare setting.