Step 1: The symptom complex of a thin, itchy, dry vulva and vagina after menopause is driven by estrogen deficiency, which thins the squamous lining and reduces secretions.
Step 2: Logical therapy gives back what is missing. Applying estrogen directly to the area rebuilds the epithelium, restores moisture and resolves the pruritus; oral estrogen or an intravaginal ring achieves the same end.
Step 3: Symptomatic antihistamines do not address the hormonal deficit, and tamoxifen actually blocks estrogen, aggravating atrophy. The rational, cause-directed choice is topical estrogen.
\[\boxed{\text{Estrogen ointment}}\]