Brief Answer:
To help you in a better way kindly upload picture of black substance.

Detailed Answer:
Hi,
Thanks for the query.

I have read your query and understand your concern.

To help you in a better way kindly upload picture of black substance on your mouth here .

Most common causes for black substance on mouth with itchy skin
1) Black Hairy Tongue due to overgrowth of bacteria
2) Bismuth products, such as Pepto-Bismol
3) smoking or using other tobacco products, drinking excessive amounts of coffee or tea and failing to follow a regular routine of daily oral hygiene
4) iron supplements

If I were your treating Doctor for this case , I would advice you
Use Antihistaminic Fexofenadine Tab Allegra at night for itching &
Diluted Mouth Wash like chlorhexidine or Betadine twice daily .

Stop any iron supplements , Bismuth products , smoking , excessive amounts of coffee or tea & maintain good oral hygiene .

Hope this information helpful to you .If you have any further questions I will be happy to help.
Regards.

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Brief Answer:
Use betadine diluted mouth wash .

Detailed Answer:
Hi,
Thanks for the follow up query.

kindly upload picture of black substance on your mouth here .

Use betadine diluted mouth wash .

Use Antihistaminic Fexofenadine Tab Allegra at night for itching. You may need a prescription for purchasing Fexofenadine.

Regards.

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