As itchy bottom is a symptom rather than a condition itself. Many cases have an underlying cause, for example: a bacterial infection – such as those that cause streptococcal infections a skin condition – such as atopic eczema, where the skin becomes red, dry and flaky haemorrhoids (piles) – swellings that contain enlarged and swollen blood vessels in and around the anus In children, an itchy bottom is often caused by threadworms. But not all cases of itchy bottom have an identifiable cause.