My father has been having issues with decreased sweating (tingling sensations all over his skin, with little itchy bumps). Ideas for diagnoses?

Decreased sweating. Neurological causes: head injuries, heat stroke, hysteria, and neurosurgical problems such as guillain-barre syndrome skin diseases that block sweat glands such as miliaria, contact dermatitis, congenital absence of sweat glands which is hereditary. Some drugs (antipsychotic drugs used to treat mental disorders) trauma to sweat glands.