It is common for preschoolers, toddlers and even infants to touch their own genitals for pleasure and to have erections. They are often curious about sexual things, and may ask questions about differences between boys and girls, having babies and having sex. Some children explore each others' bodies by "playing doctor." All of this is typical behaviour for many children. However, it can be difficult to know how to react.
If you see your child engaged in sexual exploration and play, try your best to stay calm. Young children do not know what behaviours are appropriate and they still have to learn about modesty.
The important thing is to teach them that certain parts of their bodies are private and should not be touched by others, and that they should not touch themselves in front of other people. Most parents accomplish this with a few gentle reminders. When infants or very young children touch their genitals at inappropriate times, simply move their hand away, or distract them by suggesting an activity. With older toddlers and preschoolers, explain that this is something that should be done in a private place like their bedroom or the bathroom, but do not make the child feel ashamed or guilty.
You should prepare yourself to answer the more specific questions young children will ask about sexual relations. There are many good books available in book stores and libraries that can help you introduce the topic of sex in a fun way, almost as if you were telling a story. There is a wide variety of books to choose from, so pick the ones that feel most comfortable for you.
If you are concerned that your child's sexual behaviours are not normal, talk to your child's physician. If you are in Canada, and you wish to speak with a counsellor about this, call the Parent Help Line, 1-888-603-9100.