A variety of conditions, from viral illnesses to allergic reactions, can cause red bumps to appear on the trunk of your body. Although in most cases red bumps on your trunk are mild and treatable, you shouldn't use any medications on the bumps until you know what caused them. Using the wrong treatment might make the bumps worse or cause an infection. Since it can be hard to tell the difference between bug bites and more serious skin issues, make an appointment with your health care provider so he can diagnose the cause of the bumps and offer treatment recommendations.
Some of the conditions that the American Academy of Family Physicians indicates might cause red bumps on your trunk include hives, contact dermatitis, insect bites and scabies. Certain chronic skin conditions, such as eczema and psoriasis, might also start with small red bumps on your trunk. Your doctor will use the physical appearance of the rash, along with background information you provide such as the time of onset and presence of other symptoms like itching or fever, to determine the cause of your rash.
Your age is an important factor to consider when determining potential causes of the bumps on your trunk. Some viral illnesses, such as roseola, measles and chickenpox, can cause a red, bumpy rash that starts on your trunk and spreads to your extremities, but according to the Ask Dr. Sears website, these conditions are most common in children and usually have other symptoms, like fever. In adults, shingles—a viral infection caused by the same virus that causes chickenpox in children—often starts with small red bumps and most commonly affects people over 50 years of age.
Insect bites can cause red bumps on the bodies of people of all ages, from infants to adults. The Ask Dr. Sears website suggests that bug bites might be the cause if you develop several—usually less than 20—red bumps with a bite hole in the middle. Insect bites, from pests like fleas, bedbugs and mosquitoes, can occur even in clean, pet-free houses.
If the doctor determines that bug bites caused the bumps on your trunk, you will need to eliminate the insect infestation in order to prevent future bites. Although you can often rid your home of insects such as fleas using over-the-counter home treatments, the Environmental Protection Agency recommends calling a certified pest manage professional to help you manage and control bedbug infestations.
Scabies, a skin condition caused by microscopic mites, causes a very itchy rash that can be easily spread to other people through close contact. One of the first signs of a scabies infection is itching, especially at night, accompanied by tiny red bumps clustered around your belt line, buttocks, nipples and penis. The American Academy of Dermatology urges you to seek prompt treatment in order to prevent infection from scratching and to avoid spreading the condition to others.