I take a warm or hot shower and don’t use any soap or shampoo and I get rashes on my neck. Had a rash on my chest too but its no longer, neck only?

Need exam for Dx. Many things can cause a rash on chest and neck. If you are not bathing with soap, then that can be eliminated, but clothing often has soap/softener residue. People with atopic dermatitis will often get a rash from friction of clothing around the neck or areas that perspire. Seborrheic dermatitis is common in hairy areas. Psoriasis can occur anywhere. Tinea versicolor is fungus on chest/back.