I'd just wait and try again later. Like the PP said, you aren't supposed to offer oats or wheat before 6 months as the gut is still immature and they're more likely to have a reaction. Most of these sorts of reactions are just because they aren't ready for something. Wait another month or two and try again and see if it still happens. My daughter had a severe reaction to pumpkin seeds (in the form of a butter) when she was about 7/8 months (like projectile vomiting everywhere, swollen eyes, red rashy face, she looked terrible!). The GP's advice was to wait until she was over a year to try again. When we did, she was fine. She just needed to outgrow it. If you keep having a reaction even after waiting for a couple months, I'd see your GP. A reaction to oats, while relatively rare, can be a sign of a wheat/gluten intolerance and something to watch out for. I'd say more than lilkely she just is too young to be trying anything too adventurous. Stick to the rice porridge and fruit/veg until after 6 months.