The American Academy of Allergy, Asthma and Immunology (AAAAI) estimates that 40 to 50 million people in the United States suffer from allergies.

Many plants carry pollens that can trigger allergies, but ragweed is the most common. In fact, 75 percent of people with seasonal allergies are allergic to ragweed, according to the Asthma and Allergy Foundation of America (AAFA).

The primary treatment for any allergy is avoidance, or refraining from contact with the triggering allergen. Though many drugs can help alleviate the symptoms of an allergic reaction, only avoidance can completely prevent an allergy from occurring.

While indoor allergens are not usually seasonal like many types of outdoor allergens, late summer usually sees higher levels of dust mites (due to higher humidity), molds and some pollens (which can be tracked indoors or brought in on clothes).

The airborne waste created by dust mites is the source of most dust allergies. Dust mites are microscopic arachnids (spiders) one-third of a millimeter long that live indoors in household dust. Between 100 and 500 dust mites typically inhabit a single gram of dust, though in some cases the number can soar to 19,000.

Mold and mildew allergies are usually triggered by inhaling mold spores into the lungs but may also be triggered by contact with the skin, cuts, the mouth, the nose and eyes. Eating foods contaminated with mold or mildew may also trigger an allergic reaction and may affect the digestive system.

Some people will find they are more sensitive to allergies or asthma attacks after exercising. This is because exercise, particularly in cold weather, causes the body's temperature to rise and tiny muscles surrounding the air passageways to twitch. This restricts airflow slightly, even for several minutes after the exercise is finished. Exercise also increases breathing, which brings in more pollen.

Food allergies occur in roughly 1 percent to 2 percent of adults and 3 percent to 8 percent of children, according to the AAFA. About 90 percent of all food allergies have been traced to the following foods:

• Cow's milk
• Eggs
• Peanuts
• Tree nuts (e.g., almonds, walnuts)
• Wheat
• Soybeans
• Fish
• Shellfish
  
  

Many people confuse food allergy with food intolerance, which is much more common and not as severe. Food intolerance often allows the individual to eat small portions of a problem food without experiencing symptoms. With a food allergy, even a very small portion of a food allergen can cause an allergic reaction.

The most severe kind of allergic response an individual can have is anaphylaxis. This is a severe and potentially life-threatening reaction that occurs in certain highly sensitive individuals. The condition is usually caused by an allergic reaction to certain foods, insect stings or drugs.