Stop wearing the jeans and if the rash dies down then good. If it occurs again while wearing the jeans then you probably are having a reaction to something. In the meantime, if the symptoms are causing you discomfort, try an over the counter antihistamine. If symptoms persist, contact your local doctor. Dont bother posting pics of it. A ddx on here would be a waste of time, you'd probably get 20 diagnoses and they'd all be wrong.