Without examination,I cannot confirm a diagnosis but it can be dry skin(xerosis), eczema, sweat dermatitis
, allergic reactions or seborrheic dermatitis
Eczema is a form of chronic dermatitis (rash).Allergic reaction is one of the important causes of eczema. Allergic reaction can occur to strong soaps, Solvents, chemicals, certain foods, food additives, plants, metals, cosmetics, even urine and faeces of some animals (dust mites).
Wash the areas several times with fresh water.