The full answer
It's possible, though generally low risk
If a partner has recently eaten gluten-containing food and hasn’t brushed their teeth or rinsed their mouth, trace amounts could theoretically transfer through kissing — though the amount involved is typically very small.
A reasonable precaution, not a reason to worry constantly
For people who are highly sensitive, having a partner rinse their mouth or wait a bit after eating gluten can offer peace of mind, but this isn’t typically a major or common source of significant gluten exposure for most people.
Important context
Individual symptoms, reactions, medical histories, food products, and local labeling rules can vary. Community experiences are not medical evidence.
For personal medical decisions, diagnosis, testing, or treatment, consult a qualified healthcare professional.