Is it possible to get immune to sensitive toothpaste?

Yes: Allergic reaction is a type of immunity that can be acquired over time or you can be born with it. Allergic reaction may come and go at different stage of your life. Sometimes, you have to differentiate between adverse reaction (something bad happen) vs. Allergic reaction (life threatening reaction). Check with your dentist or doctor.

No: I am not aware of any scientific study reporting immunity to toothpaste. Continue to use all oral care products as directed! i hope this helps.

Sensitivity: If sensitivity increasing it means the cause of the sensitivity has never been addressed. The toothpaste has simply masked the symptoms as the causative problem grew in intensity. Please see your dentist to try to discover the cause of this symptom and then arrive at an appropriate solution.