My son has come down with a rash on his arm, and now his nanny has it, and my husband as well. My son had blood tests taken and it came back normal, so I'm boggled about what it could be. Might it be caused by our new detergent?
I know that I personally have some kind of allergic reaction to an ingredient in certain soaps. Zest, for example, has some ingredient that my body does not agree with. Whatever the ingredient is also happens to be in some laundry detergent. Try to narrow down the offender and avoid it - that's all I do. Good luck!
Laundry detergent could certainly cause a rash but I don't think it could cause a rash that's infectious. Apparently your son picked up a pathogen that caused the rash and passed it around. Sometimes its not possible to find exactly what that pathogen was. My understanding is that most of these cases however resolve themselves fairly quickly, however. If you'd like some information on how to treat a child's rash, consider checking out this post.