Keeping your sex organs and anus clean is a good thing. Regular washing with water is usually enough. Too much soap may irritate the sensitive skin.
For girls it is particularly important to practice hygiene during menstruation. Washing carefully with warm water to remove traces of blood will keep you smelling good. Regular changing of sanitary napkins or tampons (if the bleeding is strong more than once a day) will prevent bad odours and infections. You can find good information about period hygiene on the package or on Internet under brand names such as Tampax.
Both boys and girls have a foreskin. In boys it is the thick fold of skin that can move all the way back and forth over the head of the penis. In girls the foreskin is of course much smaller, but it too must be movable over the head of the clitoris.
If the foreskin is tight, it cannot move and the head under it cannot be kept clean, which in its turn can cause infection.
When you are very young, let’s say between birth and about eight years old, the foreskin covers the head tightly, ending in a point. So even with an erection or an orgasm, the foreskin stays in its place. But as you grow bigger, the foreskin becomes looser and can move back over the head of the penis or clitoris. You can help it loosen up a little every time you wash there.
Boys collect a white substance called smegma under a tight foreskin. This can combine with urine and semen and become smelly and sometimes infected, causing a red and irritated foreskin. Girls can have similar complaints but less noticeable. Some boys and girls only discover sexual hygiene after they are eighteen. They find it difficult and painful to have sexual intercourse. If they do not seek information or are ashamed to see a doctor, they can hide the problem and try to avoid sex (and consider it dirty and hateful) for many years.
In some cases young boys have such a tight skin still at twelve years old, that they are sent to a doctor, who cuts the foreskin away. This operation is called circumcision. The same happens with girls with a tight foreskin, but they are usually much older, often after they are married, when they find sexual intercourse painful. Circumcision of boys is also performed as a religious ritual by orthodox Jews and Moslems, some days after birth or around the age of eight or nine. In some Western countries, such as The USA, the circumcision of boys is frequently performed for so-called hygienic reasons. In some parts of the world, such as Africa, girls are circumcised, too, and worse than boys. Circumcision of girls or boys without a good medical cause is a form of sexual mistreatment.