My friend is 21 and usually very healthy but recently he has developed a rash over his hands, the backs of his arms, his elbows and his feet. The rash looks like a large number of raised red bumps covering the areas mentioned, and his elbows are completely red. He says it is very itchy, has lasted about a week and at first he thought it was eczema. But he has now also developed a sore, swollen throat and is having difficulty breathing and swallowing. He doesn't have a temperature but is suffering from joint ache, headache and is finding it difficult to stay awake. What could this be?