Some are so allergic that just a drop on the skin can cause a severe reaction. Hives could be a manifestation of something you ate that you were allergic to, what I called ingestants before. Water is often overlooked. Keeping your body hydrated keeps histamine levels in control. Asthma patients can drink strong coffee in an emergency.
Bioflavinoids are wonderful.
Pineapple helps dissolve mucus. Hot peppers if you can tolerate them. It keeps nasal passages clear. Onions are a very good addition to the diet. They have anti-inflammatory properties.