An itchy body rash commonly occurs as a result of exposure to allergens or irritants. People who are allergic to poison ivy, for instance, develop a rash at the site of exposure, which spreads after the person scratches the infected area and then touches another area of the body. Some causes of itchy body rash are more severe, however, and can require medical attention.
Heat Rash
Heat rash, also called miliaria, occurs when the sweat ducts become clogged and perspiration is trapped beneath the skin. It most commonly occurs in hot, humid climates, though steam room exposure, intense exercise and certain medications can cause it to develop as well. Infants are prone to heat rash as their sweat ducts are not fully developed and can rupture easily, thereby trapping perspiration within skin tissue.
In addition to the rash, small fluid filled blisters can develop in mild cases. In moderate to severe cases, the rash becomes itchy and can be accompanied by lesions, pain and swelling. Because the sweat pores are blocked and perspiration cannot reach the surface of the skin to evaporate and cool the body, the body can become overheated.
Chickenpox
Chickenpox is a highly contagious infection caused by the varicella-zoster virus. It spreads either through direct physical contact with an infected person or by breathing in viral particles after an infected person has coughed or sneezed. The infection causes a characteristic rash, and fatigue, headache and fever are common symptoms of contagion.
Between 10 to 21 days after infection, a red rash begins to appear, usually on the stomach or face. The rash, which spreads to other areas of the body, is characterized by fluid-filled blisters and itch. An unvaccinated person can develop between 250 to 500 blisters spread over the body. A number of people who have been vaccinated will still develop a milder rash. The Centers for Disease Control and Prevention estimates that between 15 and 20 percent of vaccinated individuals will develop the rash.
A person with chickenpox is contagious for a couple of days before the rash appears. While the disease generally affects children, teenagers and adults can also contract it. In older individuals, the infection can cause severe complications, including viral pneumonia and encephalitis. Before the vaccine was created, thousands of people were hospitalized as a result of the virus and between 100 and 150 people died each year in the U.S. alone.
Measles
Since the development and widespread use of the measles vaccine, the disease is no longer common in the United States, though before the vaccine, nearly everyone was exposed to the virus by the age of 20. The CDC reports that when an outbreak does occur, it most often affects the unvaccinated, those who have traveled to areas where the vaccine is not widely used, or in areas where people are in close contact with one another, such as college campuses. The World Health Organization estimates that there were more than 20 million cases of measles in 2006 and that more than 200,000 people died of the disease. The CDC points to an increase in the number of cases in the United States as of result of parents choosing to leave their children unvaccinated, while The New York Times cites surveys that suggest the overall vaccination rate may be in decline.
Measles spreads through contact with fluids from the nose or mouth from an infected person. Sneezing, coughing and nasal dripping can spread the virus. Once contracted, the disease incubates for about 10 to 12 days, with a rash beginning a few days later. The mildly itchy rash begins around the hairline and spreads downward across the body. It generally lasts between five to six days and fades in the order that it appeared. Other symptoms include high fever, cough, conjunctivitis and tiny white spots with a bluish center, called Koplik's spots, which appear on the inside lining of the mouth.
