Human: My friend has been complaining of a rash on her back. What is the cause? Assistant: 
The most likely cause for a rash on the back is contact dermatitis, which occurs when skin comes into contact with an allergen. Common causes include detergents, soaps, and other chemicals in cleaning products, as well as plants like poison ivy or oak, metals such as nickel, and certain fabrics. It can also be caused by bacterial infections, fungal infections, or even insect bites.