The term "skin rash" can describe any change in color or texture of the skin, according to Medline Plus and the National Institutes of Health. Rashes can range from mild and localized skin irritations to widespread skin eruptions. Rashes may occur due to external factors such as weather, infrequent shampooing or alcohol-based lotions, or to internal factors such as diseases. Since a rash occurs as a symptom, treating the rash involves treating the underlying cause.
Types
Doctors use many different terms to describe skin rashes. Many times the way a rash appears helps doctors determine the type and cause of the rash. Dermatitis describes skin inflammation. Eczema, a generalized term often used interchangeably with dermatitis, describes a red, itchy and scaly type of rash. Large bumps that appear suddenly may be classified as hives. Doctors classify rashes that occur due to bleeding under the skin as purpura.
Morphology
Rashes may appear flat, such as a macule, which describes a color change less than 1.5 centimeters, or consist of bumps. A papule describes a small raised lesion less than 0.5 centimeters in diameter, while a nodule describes an enlarged papule, according to the New Zealand Dermatological Society. Doctors classify a papule or nodule that contains fluid as a cyst and an elevated thickened area of skin as a plaque.
Colors
Rashes occur in a wide range of colors. Carotenaemia, a condition caused by excessive amount of beta-carotene, cause patches of skin to appear yellowish-orange. Areas of the skin darker than normal can occur due to increased deposits of melanin, known as hyperpigmentation. Decreased amounts of melanin cause paler than normal skin, known as hypopigmentation. Doctors classify a red rash that covers much of the body as erythroderma. Small red, purple or brown dots known as petechiae, occur due to bleeding under the skin, classifying this as a purpura rash.
Common Childhood Causes
Many common childhood diseases that cause a rash can be prevented with vaccines. Chicken pox, caused by the varicella virus, causes a red, itchy rash resembling insect bites that turn into fluid-filled blisters, according to MayoClinic.com. Measles, also known as rubeola, causes a rash consisting of large, flat blotches that often run into each other. Hand, foot and mouth disease, which does not have a vaccine, occurs due to a viral infection and causes a nonitchy skin rash consisting of small red spots that turn into blisters on the hands and soles of the feet.
Medical Conditions
Several more serious medical conditions that affect adults and children can cause a rash. Systemic lupus erythematosus describes a disease that occurs when the body's immune system attacks the cells in the skin, joints, kidneys and other organs. The resulting rash appears in a butterfly formation across the face that affects approximately one-half of the patients with this disease, according to Medline Plus. Other diseases causing rashes include rheumatoid arthritis and Kawasaki disease.
Treatment
Rashes caused by disease require specific treatments for the underlying disease. More mild rashes may improve with simple at home care. Using gentle cleansers and avoiding scrubbing the rash area decreases the skin irritation. Applying hydrocortisone creams available over the counter can help reduce the redness, inflammation and itchiness of the rash.
