Food allergies can cause swelling and itching of the face, lips, mouth, tongue and extremities, and may be accompanied by hives. Symptoms range from mild to severe, and represent a response by your body's immune system.

Gluten is a protein found in wheat that can cause problems for people whose bodies can't digest it. This condition, known as gluten intolerance or celiac disease, is different from an allergy to wheat or wheat gluten that can cause sinus congestion, runny nose and a sinus headache.

Dairy is a common food allergen that can have a direct effect on your skin. Common skin problems linked to dairy consumption are generally itchy skin, hives and eczema, according to KidsHealth.org. A person with a dairy allergy has a hypersensitivity to the proteins found in cow’s milk.

As discussed by the American Academy of Family Physicians, a food allergy is an adverse reaction to food that is mediated by the immune system. Almonds, a type of tree nut, are one of the most common triggers, along with eggs, milk, soy, wheat, peanuts, fish and shellfish.

Gluten and casein are proteins that either add depth and flavor to your food or cause notorious discomfort to your body. The difference stems from your ability to digest both proteins. Gluten is found in wheat, rye and barley, while derivatives include malt, soy sauce and grain vinegar.

Flavonoids are phytonutrients in plant-based food products that often contribute to the color of the foods. They provide antioxidant activity which may play a significant role in cardiovascular health and may help to prevent against diseases such as cancer caused by free-radical damage.

For those who are sensitive to pollen, dust mites and weeds, certain times of the year may make them feel under the weather. While a seasonal allergy attack is not a true illness, the body’s response to allergens may make the sufferer feel sick.

According to AllergyEscape.com, the most common foods that cause an allergic reaction are corn, yeast, milk, eggs, soy, wheat and sugar. These common food allergens trigger similar symptoms because they cause the same immune and chemical reaction in the body.

Oysters are a type of shellfish that can be eaten either cooked or raw. According to the Centers for Disease Control and Prevention (CDC), 6.9 million people in the United States are allergic to seafood, such as oysters, shrimp or lobster.

The symptoms of seasonal allergies -- excessive mucus production, runny nose and congestion -- are caused by allergens, such as pollens or molds. Seasonal allergies do not directly cause swollen lymph nodes.

There are a number of reasons people choose to eliminate gluten -- a protein found in wheat, barley and rye - from their diets. Celiac disease is an allergy to gluten that causes irritation in the small intestine and can lead to more serious consequences including skin rash, diarrhea and depression.

Aspartame is an artificial sweetener, commonly used by people who are trying to cut down on sugar consumption. Aspartame may cause an allergic reaction in some people, resulting in gastrointestinal, respiratory and skin complications.