Red itchy rash over chest, back and behind ears might be a type of eczema
known as seborrheic dermatitis
. It is characterised by red itchy lesions covered with greasy scales and involves scalp, chest back, face , groins, axilla and flexural areas. Treatment involves application of mild steroid antifungal cream along with antihistaminics like cetirizine
. In severe cases a course of oral steroids
might be required too.
Hope that helps. Take care