You shouldn't deny others and their medical diagnosis's.
Erin has been diagnosed with a shellfish allergy.
Grant wants to throw a nice dinner party which Erin is invited to.
Grant serves nice steaks.
Grant serves lobsters even though he knows about Erin's allergy.
Erin and all the other guests have a nice time at the dinner party.
Erin is unable to eat anything at the party and feels left out.