Even when small children are running around seemingly healthy, they often have symptoms that require your attention — runny noses, coughs, low-grade fevers. A two-year-old won't blow or wipe his nose, he won't cover his mouth when he coughs, and most likely he won't tell you he wants to take it easy because he feels like he's coming down with an ailment. As an adult, you are able to recognize the initial symptoms of colds and other minor illnesses and as a result can treat these early on, often avoiding illness.
Similarly, in order to maintain your two-year-old's good health you need to know her body as intimately as your own, recognizing the first sign of illness through changes in her body or behavior. When you notice your child not being herself — whether this is reflected in her energy level, her sleeping pattern, eating habits, mood, or just by the way she looks (red eyes, dark circles under her eyes, pale skin, for example) — you can assume she's not feeling well.
When a toddler suddenly doesn't have the energy to get out of bed or he just wants to sit on the couch, there's a good chance he's sick. Lethargy can take the form not only of a need to sleep but of an inability to wake up and be alert. If your two-year-old is not moving about and seems to need you to hold him more than usual, he's likely not well and should see a doctor.
If your child tugs his ear or shakes his head a lot, he might have an ear infection. A two-year-old can't always tell you that his ear hurts, so he'll touch it rather than communicate in words. If he's crying a lot, he may also be in pain. Remember, an earache more often presents with a dull throbbing than with acute pain. Unlike a “boo-boo” that a two-year-old can recognize as an injury, earache pain may be difficult for your two-year-old to describe.
Breathing problems usually develop over time from a cold or exposure to an allergen. If your child develops a cough or congestion that evolves into difficulty breathing, meaning that he is taking shallow breaths, can't catch his breath, or is gasping for breath, you must take him to the doctor or an emergency room immediately. If your child's breathing becomes audible, that is another sign something is wrong. Not being able to catch his breath often scares a child, so try to keep him calm; anxiety or nervousness will make his breathing even more shallow. If you take deep breaths in front of him he may be able to imitate you, and that will help him calm down. Many breathing problems manifest as a cough that builds up over time. It is unusual for children to develop any of these breathing difficulties without some preceding symptoms like cough, fever, or runny nose. If your child has a cough that progresses to the point of him vomiting and having difficulty breathing, you should call your doctor immediately.
Always trust your own judgment in deciding whether to take your child to the doctor. It is always better to be concerned enough to seek help (even if nothing proves to be wrong) than to wait to seek treatment until your child is terribly ill.