You might think concussions are a risk only athletes face, but anyone can suffer from one — no matter your activity level, no matter your age.

The most common causes of concussion are falls and motor vehicle accidents and the most vulnerable groups span the ages, including the very young, the very old and men in their late teens to early 20s.

"When a blow to the head or body causes the brain to quickly move back and forth or twist within the skull, it can cause a concussion — a type of minor traumatic brain injury that results in temporary alteration of brain function," explains Dr. Kenneth Podell, a neuropsychologist and the director of the Concussion Center at Houston Methodist. "We don't actually know how common concussion is because most aren't reported, with some estimates suggesting that 9 out of 10 concussions go unreported."

Perhaps this is the case because most of us aren't quite sure when a bump to the head warrants medical attention and when it doesn't. Is a headache after hitting your head enough? Or do symptoms need to be more severe before you take action?

Dr. Podell is here to explain the signs of concussion and why it's important to be evaluated if think you might be concussed.

What does a concussion feel like?

One of the biggest misconceptions about concussions is that a person always loses consciousness. This isn't the case. Nor does the severity of impact define concussions.

"How damaged a car is after an accident doesn't necessarily tell you how injured the individuals in the car will be — the same goes for concussions," says Dr. Podell. "There are multiple mechanisms involved in a concussion, and what we're most concerned about is how quickly the brain moved inside the skull."

This isn't something you can see, of course. But there are on the order of two dozen signs of concussion to be on the lookout for.

"Concussion questionnaires can include anywhere from 20 to 25 different symptoms, and, for simplicity's sake, these can be broken down into four broad categories: physical symptoms, cognitive symptoms, mood symptoms and fatigue/sleep-related symptoms," says Dr. Podell. "These can appear right after the injury or develop very soon after."

Some of the common concussion symptoms include:

• Double or blurry vision
• Headache
• Light and noise sensitivity
• Loss of balance
• Mood or behavior changes
• Feeling mentally foggy
• Nausea and vomiting

"The most common symptom of a concussion is headache," adds Dr. Podell. "About 80% of people experience one. Whereas loss of consciousness only occurs about 10% of the time or less."

What (not) to do after experiencing a concussion

If you've suffered a blow to the head or body and are worried you've suffered a concussion, there are a few things you should do — as well as a few you shouldn't.

"No matter how hard of an impact you take to the head, it's always important to be evaluated if you notice signs," recommends Dr. Podell. "Concussions are a multisystem injury, affecting everything from cognition to balance to mood to your neck, all treatable. A quick and accurate evaluation by a concussion specialist or physician can help pinpoint the deficits and lead to treatment options that will help speed up recovery."

Additionally, people who have had a concussion are more likely to have another one. It's very important to take steps to avoid a repeat head injury while concussion symptoms are ongoing. This is advice your doctor can provide.

A few more do's and don'ts if you're worried you may have a concussion:

• DO pump up the hydration
• DON'T drink alcohol
• DO be sure to feed your brain carbohydrates as it recovers
• DON'T take any aspirin or a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen or naproxen
• DO take acetaminophen for pain relief
• DON'T drive while experiencing symptoms
• DO monitor symptoms and know the signs to head to the emergency room

Dr. Podell stresses the importance on only using acetaminophen (Tylenol) for the first two days following a concussion to treat headache or neck pain.

"NSAIDs like Motrin, Advil or Aleve are problematic because these medications have blood-thinning properties and, in the slight chance there is also a brain bleed, we don't want to worsen it," explains Dr. Podell.

As for how long to monitor concussion symptoms, Dr. Podell recommends three to six hours immediately after the injury. This is likely why you've probably heard that a person shouldn't be allowed to sleep afterwards.

"If symptoms aren't worsening after several hours, it's typically fine to go to sleep," adds Dr. Podell.

You'll need two to three days of physical and cognitive rest, but this doesn't mean sitting in a dark room doing nothing. A gradual return to physical and mental activities is often the best way to recover — the Goldilocks approach of neither too much nor too little, adds Dr. Podell.

Reasons to head straight to the ER after a head injury

If you're unsure whether you have a concussion, Dr. Podell says it never hurts to get evaluated so you're sure.

"Whether through urgent care, your primary care office or a specialist, a simple rule of thumb to follow is when in doubt, get checked out," says Dr. Podell.

That said, there are situations that warrant heading straight to the emergency room.

The red flags that signal immediate medical attention is needed for concussion include:

• Loss of consciousness
• Falling from higher than six feet
• Bloody or clear discharge from the ears
• Loss of sensation or persistent numbness in an area of the body, particularly in the face, shoulder or arm
• Vomiting two or more times
• Bruising of the back of the head, specifically the base of the skull where it meets the neck
• If you take a blood thinning medication
• Symptoms such as dizziness, imbalance, neck stiffness and irritability significantly worsen over the following three to six hours

"In these cases, we're either concerned the brain injury could be more than minor, a spine injury or the possibility of a brain bleed, which are medical emergencies," warns Dr. Podell.