Your son fell in the kitchen and banged the back of his head on the floor. He didn’t lose consciousness, and after some tears, seems OK. Should you worry about a concussion? The answer is yes.

Concussions can be tricky because symptoms don’t always happen right away—some take hours, days, weeks, or even months to appear. And fewer than 10 percent of people with concussions actually lose consciousness. So even if you don’t pass out, you could still have injured your brain.

Luckily, most people with concussions recover quickly and completely. Although recovery can be slower for young children, teens, and older adults. Symptoms usually fall into four categories—watch for them:

Thinking/remembering: Can’t think clearly, difficulty concentrating or remembering new information, feel slowed down

Physical: Headache, blurry vision, nausea or vomiting, dizziness, sensitivity to noise or light, balance problems, fatigue

Emotional/mood: Irritable, sad, nervous or anxious, more emotional

Sleep: Sleeping more or less than usual, having trouble falling asleep

As always, it’s important to contact a doctor right away if you think you or someone you know may have a concussion.