Infulaphobia
A specific type of germaphobia in which you have the fear of eating/drinking after people or anything or anything that has touched their mouth. Thinking about the other's saliva mixing with the food then eating it grosses infulaphobic's out and forces them to stop eating if the other person used their utensil or has placed anything, that has been in their mouth, on their food. It doesn't have to just be spit, sometimes, in rarer cases, infulaphobic's don't like to eat common snacks such as chips or goldfish if the other has touched them.
Alexandra politely declined Dillan's offer to sip a taste of his beer after imagining his spit mixing with the drink and swallowing it, instead, she ordered one of her own to try; one of the downsides of having infulaphobia.