Take any over-the-counter antihistamine with cetirizine, fexofenadine or loratadine. Start with one a day if this doesn't go away, increase it to twice a day. If this doesn't help go see your doctor.
If you have a rash and poison ivy is a possibility, use Hydrocortisone cream. Rarely the start of shingles can start as an itch. For this you should see a doctor within 72 hours.
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