Scarlet fever, also known as scarlatina, is a condition caused by streptococcus pyogenes bacteria, the same bacteria that causes strep throat. It is most common in children between the ages of 5 and 15, and although scarlet fever is highly contagious and once considered incredibly dangerous, treatment is simple and involves a regimen of antibiotics. Among the myriad symptoms of scarlet fever is an itchy rash, which can be treated in a variety of ways.
In addition to an itchy rash, the symptoms of scarlet fever include a red rash with the consistency of sandpaper; red lines known as Pastia's lines that can occur in the folds of the skin of the groin, elbows, knees, neck and armpits; a red and bumpy tongue, often accompanied by a white coating; flu-like symptoms, such as fever, chills, nausea, sore throat, vomiting and headache; and enlarged lymph nodes of the neck. A doctor should be consulted at the first sign of a rash or any severe flu-like symptoms, and once a diagnosis of scarlet fever is confirmed, treatment should begin immediately.
Although the itch will most likely subside as you're taking antibiotics, short-term relief can come in the form of oral antihistamines, such as diphenhydramine and clemastine fumarate, and topical over-the-counter calamine lotion. Although rare, an allergic reaction to calamine lotion can occur, characterized by localized swelling or an exacerbated skin rash, and so calamine lotion should be applied only over small areas and only as needed.
Other simple ways to help alleviate an itch are to take a warm bath or apply a cold compress to the affected area, and, most importantly, do not scratch it. If you scratch the itch, you run the risk of making it and the rash worse in the long run. Additional help can be found by avoiding itchy fabrics, such as wool, and avoiding excessive exposure to the sun.