Experiencing a headache and nausea after eating a meal can be frightening, particularly if it happens consistently. Any one of a number of underlying health issues could be to blame, particularly a food allergy or a food intolerance. Not all of the potential problems are serious, but many of them can be -- particularly food allergies -- so it's important to consult a doctor to find out the exact cause.
A common cause of headaches and nausea after eating is a food allergy. Food allergies occur when the body reacts to a specific food as if it were an invader. The immune system kicks in and causes the typical symptoms of an allergy, which can include a headache, nausea, itchy skin, tingling around the mouth or a rash. A serious food allergy can cause shortness of breath, chest pain and swelling of the airway to your lungs. Your body can also go into shock, which can be fatal. Common food allergens include milk proteins, wheat, peanuts, tree nuts -- such as almonds or walnuts -- soy, fish and shellfish.
Having a food intolerance simply means that your digestive system cannot properly break down a specific food. A food intolerance does not involve the immune system, although some of the symptoms of a food intolerance are similar to a food allergy. Symptoms of a food intolerance are primarily related to digestion and can include gas, nausea, cramping, bloating, diarrhea or vomiting. You might also experience a headache or a sense of irritation. Any food can cause a food intolerance, but common triggers include wheat, gluten, eggs and coffee. The most common food intolerance is lactose intolerance, according to the Cleveland Clinic. Lactose intolerance is caused by a problem digesting the sugar -- known as lactose -- found in milk.
A migraine is a common type of headache that is often accompanied by nausea, vomiting or a sensitivity to light. You might also experience visual disturbances just before a migraine. The cause of migraines is unclear, but they can be triggered by a variety of stimuli, including food. Common triggers for migraines include foods that have been processed, fermented, pickled or marinated, as well as foods that contain tyramine -- including aged cheese, red wine, smoked fish and figs. Chicken livers and some types of beans also contain tyramine. Foods commonly associated with allergies -- such as nuts, peanuts, chocolate and dairy products -- can also cause a migraine, as can avocados, onions, bananas and citrus fruits. Meats that have been processed with nitrates, such as bacon or salami, are also common culprits.
Experiencing a headache and nausea after eating can also be a sign of other, often serious, diseases. For example, high blood pressure -- or hypertension -- is often symptomless, but eating salty foods may trigger a headache and nausea. Eating sweetened foods may cause a similar reaction if you have diabetes. You might also experience a headache and nausea if you have an underlying digestive disorder. As many health issues can lead to headaches and nausea after eating, it's vital to consult a doctor as soon as possible to get a proper diagnosis.