Brief Answer:
Most probably nothing harmful, hydrogen peroxide in water, chlorhexidine

Detailed Answer:
Hi
Welcome to HCM
I have gone through your query.
It is difficult to diagnose exactly without examination, so kindly upload the picture to help you out.
A yellow discoloration of your tongue — is usually a temporary, harmless problem. It usually occurs as a result of a harmless buildup of dead skin cells on the tiny projections (papillae) on the surface of your tongue.

Medical treatment is not usually required, if it is bothering you try gently brushing your tongue with a solution that is 1 part hydrogen peroxide and 5 parts water once a day. Rinse your mouth with water afterward several times.

Apart from these kindly reduce smoking (if you smoke), reduce the amount of coffee and tea, avoid chewing tobacco.
Eating sour food, which stimulate the production of saliva. Oranges, unripe mangoes, or citrus fruits are some examples of sour foods.
Use antiseptic solutions like CHLORHEXIDINE mouth wash twice daily after food.This will kill the offending bacteria and help you get rid of the problem.

Apart from these I would like to know are you taking any drug, had you suffered from upper respiratory tract infection or fever recently, is there any burning sensation in throat, do you have acidity problem.

Hope this helps.
I'll be glad to address your further questions.
Take care.

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