You are experiencing a typical symptom of FMS and it is one that can drive you nuts! The release of mast cells is responsible for the bulk of your annoying symptoms. Itchy eyes, facial flushing, flushing of the upper torso, and rosacea are one of many outward manifestations of this single process.
Minimize your exposure to heat, alcohol, spicy foods, hot drinks, and hot baths. Cleanse skin with lukewarm water only, pat your skin dry. Do not use any botanicals containing irritating ingredients such as citrus oil or mint. Check your shampoo for any of irritating substances, including alcohol. Pantene works pretty well for me.
I've heard that taking a warm bath in epsom salts, sea salts, and baking soda (1 cup each) helps. Take a shower aftwards to wash off the salt. Use Lac-Hydrin or Aquafor lotion on your skin. Use Benadryl at night to help you sleep.