The first thing you need to do is stop eating or using whatever is causing the allergic reaction. If the reaction happens a few days before your wedding Dr. Wechsler recommends using hydrocortisone cream twice a day and taking Benadryl at night or trying a whole-milk compress for 10 minutes twice a day.
For allergic reactions the day of your wedding, use the hydrocortisone cream and then cover up redness by canceling it out entirely. "The opposite of red is green, so apply green tinted concealer on the red area," says makeup artist Linsey Snyder Wachalter. The combination will create a flesh-toned hue.
"A good quality tinted moisturizer naturally has green/yellow undertones and also provides moisture to dry skin; Laura Mercier has a terrific one and is a great option to take red out and quench thirsty skin," she adds.