For example, you are allergic to grass pollen, you would get regular grass-pollen vaccine shots. We know this works for patients with hay fever and allergies to cats. It is also considered for patients with severe allergies or allergies that do not respond to the usual medications.
Symptoms start to improve soon after the therapy begins and continue improving after it stops.
In fact, patients who stop getting the shots still have noticeably lessened symptoms for 3 years after stopping the shots and sometimes even longer. This makes us think that the shots must make long-term changes in the immune system. Possibly immunotherapy may help people who tend to get allergies avoid developing new ones. The immune system has many other types of cells that play important roles in the body, like fighting off infections and destroying cancer cells. Fortunately, immunotherapy only seems to affect the types of reactions that result in allergies.