A rash, caused by either an allergy, an infection or an autoimmune disorder, can cause red spots on the stomach, according to Healthgrades. A rash is also sometimes caused by medication, stress or extreme temperatures.
Cosmetics, dyes, industrial chemicals, metallic substances and poison ivy are some of the things that can trigger an allergy-related rash on the stomach. Eczema can also cause a scaly or blistering allergic rash, and food allergies or an allergic reaction to an insect bite can also cause red spots on the stomach, states Healthgrades. Infectious diseases that can cause a stomach rash include chickenpox, impetigo, Lyme disease, measles, mumps and strep throat.
Some autoimmune disorders that cause a stomach rash include psoriasis, rheumatoid arthritis, systemic lupus erythematosus and Kawasaki disease. Kawasaki disease is a rare but serious pediatric disorder that causes inflammation of the blood vessels, high fever, mucus membrane changes and a rash, notes Healthgrades.
In some instances, a stomach rash may be a sign of a life-threatening condition such as anaphylaxis or allergic purpura. Patients should consult their doctors when a stomach rash appears to rule out any serious diseases. Measles, for example, can lead to serious complications such as hearing loss, miscarriage or brain infections if left untreated, according to Healthgrades.