Both food sensitivities and intolerances could be to blame for your frequent bouts of nausea, especially if your symptoms feel vague or are otherwise difficult to explain.

"Unlike a food allergy, food intolerances usually have a gradual response from the body and may only occur if you eat a lot of the food or eat it frequently," registered dietician Lorraine Chu, MS, RDN, tells Bustle.

Do you feel nauseated after eating dairy products? Or after having a glass of wine? If so, "you may be lacking an enzyme needed to digest a certain food, such as lactase for dairy products," Chu says. "It may also be a sensitivity to food additives, such as sulfite, which is used to preserve foods such as dried fruit, canned goods, and wine."

Food sensitivities can be tough to diagnose, but paying attention to what you eat and how it makes you feel can help. "You can start by tracking what and how much you ate that day, any symptoms you're experiencing, and what time they started," Chu says. "It may also be helpful to share your diary with your doctor or dietitian to help get to the root of your problem."

"Women who have endometriosis [...] frequently have nausea and discomfort associated with their menses," Brian A. Levine, MD, MS, FACOG, a double board-certified OB/GYN and reproductive endocrinology and infertility specialist, tells Bustle.

So if you tend to feel nauseated right around your period, this might explain why. "The mechanism is not completely understood," Dr. Levine says, "but is thought to be due to endometriosis implants on the bowel and possibly the stomach."

Nausea could also be due to a simple case of motion sickness. "Different parts of our body send signals to our brain that give us a sense of balance, including our inner ear, eyes, skin, and muscles," Montemayor says. "Sometimes, these signals contradict each other, causing motion sickness/sense of imbalance which can be followed by nausea."

If you're prone to motion sickness, you may find that it doesn't take much to make you feel sick. "Some people are more prone to motion sickness than others and it is unclear why, but it may be hereditary," Montemayor says. "A lack of sleep can also increase the risk of motion sickness."

Nausea that's due to hormonal fluctuations can be rather intense, as well as difficult to pinpoint. "Hormones act as chemical messengers that help control many functions in the body and hormonal changes or imbalances may trigger nausea," Montemayor says. "This is why women who are pregnant, on their period, or going through menopause commonly report dizziness, morning sickness, and/or nausea."

"Certain medications may cause nausea because they affect the parts of our body that signal balance or irritate the digestive tract," Montemayor says. If you have nausea that you just can't explain, and are taking a medication, tell your doctor. They may be able to switch you to one that isn't as nauseating.

If you take birth control and experience nausea, there's a chance the two are connected, especially if you're always getting new pills. "Frequently, generic brands are switched by pharmacies due to changes in formularies," Dr. Levine says. "Although similar in formulation, the binders tend to vary, and this may lead to different sensitivities. Women also do have some associated nausea the first time they start birth control."

According to Dr. Hughes, one symptom of gastroesophageal reflux disease (GERD) is nausea. And until you treat the underlying cause, it's unlikely to go away.

GERD is a digestive disorder that affects the lower esophageal sphincter (LES), which in turn allows the acidic contents up your stomach to come back up into the esophagus, leading to nausea. Other symptoms include pain in the chest — otherwise known as heartburn or acid reflux — and a bitter taste in the mouth.

Vertigo is often caused by a problem with the inner ear. It can make it feel like you're spinning, or like the room around you is spinning. And that, unsurprisingly, can lead to nausea, Dr. Hughes says.

Since anxiety and panic attacks can cause you to feel nauseated, don't overlook them as a possible cause for your frequent queasiness, Dr. Hughes says. By treating the anxiety itself — possibly with the help of a therapist — you will likely start to feel better.

If you feel nauseated easily, there are quite a few reasons why that could be. While there are numerous over-the-counter treatments for nausea and ways to ease your symptoms, your best bet is to let a doctor know. They can go down the checklist of all the causes — from your inner ear, to your hormones, and beyond — and help get you back to your old self again.