A week before the party, phone the host and explain your child is gluten intolerant and what that means.
Enquire what the host is planning to serve at the party and ask if it is okay to bring something which is gluten-free.
Bring something to share- for example: a plate of gluten-free sausages, a gluten-free pizza, a bowl of popcorn, a plate of gluten-free biscuits or some gluten-free cupcakes.
If time is a problem, then pack a lunch box for your child with lots of special treats and with similar party food.
Talk to your child. Be open and honest about the party and what they can expect. Explain that most of the food will contain gluten and that they must stick to only gluten-free food. Rehearse with them which foods are likely to be safe for them to eat. Where possible let them explain to other children why they can’t eat gluten but be on hand and keep a watchful eye on the proceedings- at least initially.
Make sure you feed your child before the party. They are less likely to be tempted if they are not hungry.