Brief Answer:
Personal care & doctor's advise to find /treat the root cause.

Detailed Answer:
HI xxxxxxxxxxxx
Thanks for the query on healthcare magic platform.
I have read your query carefully & would try to satisfy you by explaining various causes.
You have a red spot under tongue with excessive salivation & metallic taste.
* Red spot can be caused by -
- Injury to the part ( in form of very hot drink/ spicy food/ hard to chew food / irritation because of broken teeth or ill fitting denture.
- Allergy,
- infection - ulcer secondary to infection as a side effect of antibiotics taken for infection.
- Neurological involvement can cause bell's palacy.
* Metallic taste can be there due to various causes including smoking / aging/ breathing through mouth / B complex deficiency, due to Infections any where in body treated by antibiotics / Digestive problems / Dietary deficiencies./ Injury to taste buds .
*Excessive salivation is seen As a reaction to any of above conditions which irritate mouth mucus membrane
** Now considering all the symptoms together & absence of any other accompanying symptoms-I feel you mostly have -
-Injury/ infection/ Ill digestion/ B complex deficiency causing ulcer under tongue as a cause of your problem.
1. In this scenario I would advise you to consult your family physician for evaluation of the case. He would examine you/ get you investigated as per need/ start treatment Or may refer you to Dentist/ physician/ gastroenterologist .. for expert advise.
2. Personal care-
- Keeping the mouth clean by regular gargling with warm water.
- Application of Boroglycerine mouth paint to the red spot helps.
- Try to have good bowel movements in case you are constipated.
- B complex/ Folic acid would relieve the symptoms.
- Eat bland diet to avoid further irritation.
I hope, the answer was both informative & useful to you. Any follow up query is welcome.
Thanks.

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