I find it hard to believe that the saliva is causing that. It might be some sort of a bacterial infection in the mouth which causes the PH condition in the mouth to go to the acid levels, or it's causing an infection to the tongue and that is making the burning sensation.
Burning Tongue Syndrome occurs in several conditions. Dry mouth from medication, oral thrush (fungal infection), diabetes, menopause, and anxiety or depression are some. See your dentist or doctor for diagnosis.
I doubt that it is your saliva that is burning your tongue. More likely it is something IN your saliva such as some spices or a medication that has changed the taste of it. Eat bland foods for a day or two and see if that helps. If not, see a doctor.
you might have an excess amount of bacteria with dry mouth. Usually with a dose of antibiotics this could happen and then your tongue feels like the saliva is causing it to burn. In reality it is the bacteria in the saliva that causes the burning sensation. You should stop the antibiotics and seek professional hep.