Likewise my mom, i hv severe eczema in genital area for years;always itchy when sweating, skin in this area are darkened.is it hereditary? medicine?

Eczema: Eczema is a multifactorial disease. Many genetic abnormalities might play a role in its pathology either hereditary or new mutation. One of those that has been identified to be associated with severe eczema is a mutation in a skin protein called filagrin, which helps maintaining the skin integrity. Regardless, moisturizer ; antiinflammatory meds are main treatment. See an allergist ordermatologist.