Haritaki is excellent for the treatment of mouth ulcers.

The recommended procedure is to put the dry haritaki powder into the mouth directly on to the ulcer. The wetness of the mouth causes the powder to become wet and the haritaki to become effective. As the powder is easily swallowed I recommend that you apply it every hour for 8 hours.

How haritaki works in the mouth.

Haritaki has strong anti-bacterial properties and these go to work on the ulcer, reducing the number of germs present.

What causes Oral/Mouth Ulcers?

Mouth ulcers are caused by either:

bites and cuts to the inside of the mouth
Stress and anxiety
Foods that are salty
Foods that are sweet
Smoking
Sodium lauryl sulphate in toothpaste

Alternative treatments using Haritaki for mouth ulcers

Haritaki can also be used as gargle to treat these oral ulcers and sore throat.

More information about mouth ulcers from this source:

Self care
Things you can do to speed up healing include:
applying a protective paste recommended by your pharmacist
using a soft toothbrush to brush your teeth
using a toothpaste that doesn’t contain sodium lauryl sulphate, as this may be irritating
avoiding hard, spicy, salty, acidic or hot food and drink until the ulcer heals
using a straw to drink cool drinks
avoiding things that may be triggering your mouth ulcers – see causes, below
Pharmacy medicines
You can buy several types of mouth ulcer treatment from a pharmacy. Speak to your pharmacist about the best treatment for you. Options include the following:
Antimicrobial mouthwash may speed up healing and prevent infection of the ulcer. Children under two shouldn’t use this treatment. It also contains chlorexidine gluconate, which may stain teeth – but this may fade once treatment is finished.
Painkillers are available as a mouthwash, lozenge, gel or spray. They can sting on first use and your mouth may feel numb – but this is temporary. Mouthwash can be diluted with water if stinging continues. Children under 12 shouldn’t use mouthwash or gel. Mouthwash shouldn’t be used for more than seven days in a row.
Corticosteroid lozenges may reduce pain and speed up healing. These are best used as soon as the ulcer appears, but shouldn’t be used by children under 12.

Obviously we recommend using Haritaki before using any of the pharmacy medicines.

Here is a link to more benefits of Haritaki