ETA: Now that I've read the other responses, I still think there is an element of drama, and hence my belief that it was rude, because of this part of the mom's statement…'and it isn't fair to make him watch.'
If the child cannot have cake for whatever reason, the mom is certainly within her rights to remove him. The problem is her timing and that last comment. At any time during the party, she could have told the hostess he can't have cake and then slipped out quietly. Knowing she was going to do this, she could have thanked the hostess prior to departure or even called the hostess later to thank her. But the inclusion of the statement about the fairness of it all smacks of drama.
As I said in my original response, I hope she's just new to this and will develop better strategies in the future.
ORIGINAL:
Yes, it'd odd, AND it's rude.
I'm saying that as a mom of a child with severe allergies. My son has outgrown most now but is still severely allergic to tree nuts. We've had to do the Epi-pen and ER trip for anaphylaxis, so I truly know and appreciate how serious allergies are, and I'm a big advocate for food allergy education.
Since my son was so allergic to so many things, he learned early what he could and couldn't have. I taught him that he'd get really sick if he ate _________ (whatever it was). There were many birthday parties where he couldn't have cake and ice cream. Was he sad at first? Yes, of course! He was a little kid! The important thing, however, was that he LEARNED. You have to teach kids with allergies that there are certain things they cannot have, and that's just the way it is. It might not be fair, but it's reality, and as a parent you have to teach them that.
Depending on the event, I'd either bring a special snack or I'd tell him he could have one of his treats later at home. He learned. My sister-in-law does the same thing for my niece, who, at 11, still has not outgrown her nut and dairy allergies. Our kids don't stop going to parties. They adapt.
For this mom to make a scene in front of everyone and steal the birthday boy's moment was just wrong. Maybe she's new to being a mom with an allergic kid, so I hope she'll learn. Additionally, she deprived her son of a very important learning experience----that there will be things at various events in life that he just can't eat.
It is vital that children with allergies to learn this lesson, and it becomes more important as kids move into the school years where they are not constantly supervised by parents. They have to be able to say, "I can't eat that" and be okay with it. Especially when otherwise well meaning adults say, "oh are you sure you can't just have one little slice?" It happens, and he needs to be ready to say no, but he won't learn that if mommy keeps swooping him away whenever something might make him sad.
I don't want to seem unsympathetic, but her child needs to learn this lesson, and she needs to learn appropriate proactive parenting. There is a way to advocate for your child and educate people about allergies without making a scene.
For your parties, simply ask the teachers for a list of the food allergies in your class and go from there. Most schools have no nut policies, but there are other common allergies to be aware of. Ask the teacher what kinds of treats the kids who have allergies CAN have and provide those as an alternative. When I brought doughnuts for my son's class for his birthday, I brought a small package of oreos for the child who couldn't have doughnuts. It was the one treat he could have.
For your party at home, just ask the parents. If any kids with allergies will be attending without parents there, make sure they bring their allergy action plans and emergency kits (antihistamine and Epi-pen or similar injector if they have one) and be sure someone there knows how to use it. I promise, it's not as complicated as it sounds!
Food Allergy Research & Education at www.foodallergy.org is a great resource for anyone dealing with food allergies. (It's not my website, and I have no business relationship with it----have just found it really helpful). Check that out for additional ideas, and your parties will be problem-free. Well, at least allergy problem-free! : )
Thanks for showing concern and care for those with allergies! Good luck with your parties!
J. F.