Scarlet fever
Scarlet fever is an uncommon reaction to a bacterial infection, usually of the throat ('strep throat'). The bacteria (streptococcus) make poisons (toxins) which circulate in the blood and cause a fever, a fine raised rash on the neck, chest, under the arms, in the elbows and on the inside of the thighs.
For further information please see the scarlet fever page at Health Direct.