What can cause redness and raised bumps on the back, chest, abdomen and neck?

Emergency warning: If there is difficulty breathing, swelling of the face or throat, fainting, sudden vision changes, severe headache, high fever or uncontrolled bleeding, seek emergency medical care immediately. Redness and raised areas on the back, chest, abdomen and neck can have several causes. Common possibilities include allergic reactions, contact dermatitis, urticaria (hives), skin infections (bacterial or viral), reactions related to heat, sweating or pressure, drug-related skin reactions, and less commonly systemic conditions. Determining likely causes depends on when the symptoms started, how widespread they are, whether they itch or hurt, any new medicines or topical products, past allergy history and any accompanying systemic signs (fever, breathing symptoms, widespread swelling). Guidance: If there are no emergency signs, initial evaluation by a dermatologist is often appropriate. If an allergic cause is suspected, consider Immunology and Allergic Diseases. If infection or a systemic illness is possible, Infectious Diseases and Clinical Microbiology or Internal Medicine may be involved. Go to Emergency Medicine for urgent signs. Low-risk home measures for comfort (not treatment) include keeping the affected area clean and cool, stopping new cosmetics/cleaning products or recently worn garments/accessories, avoiding vigorous rubbing or scratching, photographing the skin to track changes, and ensuring adequate fluids and rest. If symptoms do not improve within a few days, spread, or worsen, seek medical evaluation. Your clinician may order tests or refer you to a specialist as needed. This page is for general guidance and not a medical diagnosis or treatment plan.