A rash around the neck or chest can occur for a variety of reasons including eczema, bug bites and psoriasis. Contact with clothing dyes, detergent, soap, latex, rubber and poisonous plants can also cause a rash, according to Healthline. A rash could also be a side effect of a drug.
The physical manifestation of the rash helps health care providers determine a more specific diagnosis, explains FamilyDoctor.org. Rashes can take a number of different forms, such as blisters, red patches, clusters of bumps, or tender and swollen areas of skin. Depending on the severity of the rash and its cause, the rash can either be treated at home with over-the-counter medications or by a doctor.