Ans: Many people who have certain types of allergies do not realize when they have covid. This is because the symptoms of both of these are very similar to each other. However, unless you have milk allergies, you will not have diarrhea. This is something that most covid cases have experienced. The loss of smell or taste when you have flu or allergy is very mild. But in the case of covid, there is a complete loss of these two senses.