Red spots on the skin can be caused by infectious diseases such as chicken pox, shingles or rubella, points out MedicineNet. They can also be a manifestation of an allergic reaction to poisonous plants or other allergens.
Shiny, red spots on only one side of the torso could indicate a case of shingles, a disease caused by the herpes zoster virus that is related to chicken pox, explains MedicineNet. Shingles can be very painful, but the condition only occurs in people who had chicken pox as children. Chicken pox itself consists of red, itchy, fluid-filled spots that typically cover the face, chest and back.
Exposure to poison ivy and other poisonous plants can cause a rash that appears as a series of red blisters wherever the skin touches the plant. It takes about three weeks for the rash to go away, and the body does not develop any immunity to the poisonous plant. Hives manifest as red spots on any part of the body and are part of an allergic or immune-system reaction. Although they are very itchy, they only last about eight hours and go away on their own, notes MedicineNet.
Rubella, also known as German measles, is a childhood disease that spreads red spots all over the torso. According to Everyday Health, rubella also affects young adults who have not been vaccinated. It is dangerous for pregnant women to contract rubella.