Excessive exertion during defecation increases the pressure on the vein wall, which dilates the veins. In more severe cases, exertion causes the internal haemorrhoidal lumps to move out of the anus with the mucosa that covers it, causing itching, pain, and additional urge to defecate.
Frequent defecation also take too much strain and dilate the veins.
A diet low in fibre, high in carbohydrate, fatty, spicy and intensely spiced foods, and insufficient fluid intake can lead to haemorrhoids.
Increased abdominal pressure in case of an overweight individual may be the cause of haemorrhoids.