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You need to prevent constipation
by eating fresh fruits and green leafy vegetables, also you can take Ispaghulla husk 2tsp in one glass of warm water when constipated because this will allow smooth passage of stools and prevent further damage to fissure. Drink plenty of water. It is best you get it examined by a Surgeon as some acute fissures will heal but some chronic fissures will be painless but will not heal and surgery may be required.