tenebrica

A combination of heat and cold! Use one of those bug pens (or a cotton ball dipped into very hot - about 70°C - water) and press it against the bite for about 10-15 seconds. Repeat if necessary.

Afterwards, use ice, frozen peas, a cool pack, or a cloth saturated with a mixture of vinegar and cold water, and apply it to the bite.

As someone who is sensitive to MSG, tomatoes, parmesan etc. ALSO affect me in similar ways, albeit usually less severely.