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The swelling part in your mother might be separate from the itching she is getting.You should consult a dermatologist
for her itching ,but for swelling she should consult a physician.
Before that she can use a good moisturizing cream 3-4 time a day over both legs to relieve itching .She can also take cetrizine
tablets for the same.The best time to apply a moisturizer is just after bath on wet skin.