Here's how to ruin a party in just one step. A lot of planning is involved with any party – making a list of food, drinks, party supplies, and more. This person had their party all planned out. They invited their friend group , and mentioned more than once they have a severe allergic reaction . However, once the party actually kicked off, barely an hour passed before someone broke this one critical rule. How hard is it to avoid someone's serious allergies if you're already aware of them? As com…