Sneezing, runny or stuffy nose, itchy eyes, nose, or mouth? These are signs that you may have allergic rhinitis, a condition that affects as many as 60 million Americans. Allergic rhinitis, like skin rashes and other allergies, develops when the body’s immune system becomes sensitized and overreacts to something in the environment that is usually harmless for most people. Allergic rhinitis is commonly called hay fever.

If you have frequent shortness of breath, coughing, or a whistling wheezy sound in your chest when you breathe, you may have asthma—a chronic condition that results in inflammation and constriction of the bronchial tubes, the passageways that allow air to enter and leave the lungs.

Sinus disease is a major health problem affecting over 30 million people in the United States. Americans spend more than $1 billion each year on over-the-counter medications to treat it. Sinus disease is responsible for 16 million doctor visits and $150 million spent on prescription medications. People who have allergies, asthma, structural blockages in the nose or sinuses, or people with weak immune systems are at greater risk.

Most allergies cause mild to moderate symptoms, such as watery eyes, runny nose, or rashes. But in some cases, allergies can cause a life threatening, potentially fatal allergic reaction known as anaphylaxis. Allergies to foods, insect stings, medications and latex are most frequent allergies associated with anaphylaxis.

More than 50 million Americans have an allergy of some kind. Food allergies are estimated to affect 4 to 6 percent of children and 4 percent of adults, according to the Centers for Disease Control and Prevention. Food allergy symptoms are most common in babies and children, but they can appear at any age. You can even develop an allergy to foods you have eaten for years with no problems. Learn more about the types of food allergies.

Insect stings typically result in localized reactions with pain, swelling and redness confined to the sting site. More severe reactions include symptoms appearing over a wider area (for example, swelling of your whole arm if you were stung on your wrist) or affecting other parts of the body from where the sting occurred. Allergic reactions to stings can occur even after many normal reactions to stings and at any age. It has been estimated that potentially life-threatening allergic reactions to insect venom occur in 0.4 percent to 0.8 percent of children and 3 percent of adults. Thousands of people are stung by insects each year, and as many as 90–100 people in the United States die as a result of allergic reactions.

Eczema, also known as atopic dermatitis, is a chronic, non-contagious, inflammatory skin condition characterized by itching, redness, and scaly rashes. Eczema comes and goes over time. It results in very dry and sensitive skin, and can be made worse by exposure to many different things, including allergens such as pet dander or dust mites. Other common triggers include soaps, detergents and lotions with heavy fragrances. Exposure to perfumes and cleaning products can also irritate eczema. For some people, weather changes (especially dry winter air) make eczema worse. Eczema is particularly common in infants, and an estimated 10 to 20 percent of children have eczema. It is not contagious and is often hereditary. About 60 percent of those with eczema will experience symptoms by age 1, and another 30 percent will experience symptoms by age 5. Children born into families that have a history of allergic diseases such as asthma or hay fever are at an increased risk for developing eczema. Eczema is considered to be part of the “atopic march.” The atopic march involves the diagnosis of eczema, food allergy, allergic rhinitis, and asthma, typically in that sequential order. Although the majority of children outgrow eczema, for adults who continue to suffer, it is a serious condition. Adult eczema is a chronic condition that involves inflamed, red, itchy patches of skin that can erupt in oozing flare-ups. Different areas of the body can be affected for adults, including face, hands and even eyelids. The itching for adults can feel unbearable as flare-up can affect skin all over the body. There are treatments and medications which can help control some of the itchiness and pain caused by eczema.

Hives, also known as urticaria, affects about 20 percent of people at some time during their lives. Episodes of hives can be triggered by many substances or situations and usually start as an itchy patch of skin that turns into swollen, red or white itchy welts. The itching may be mild to severe. Scratching, alcoholic beverages, exercise and emotional stress may worsen the itching. Acute (short-lived) episodes of hives are often part of an allergic reaction. Chronic urticaria (long term hives typically lasting longer than 6 weeks) are most often not caused by allergies, but in some cases can be a sign of an underlying health problem such as thyroid or autoimmune disorders.

The term angioedema refers to swelling in the deeper layers of the skin, often seen along with urticaria (hives). Angioedema most often occurs in soft tissues such as the eyelids, mouth or genitals.  It is called "acute" if the condition lasts only a short time (minutes to days). Acute reactions can be caused by an allergic reaction to medications or foods. Chronic recurrent angioedema refers to when the condition lasts long period of time. It most often does not have an identifiable cause. Hereditary angiodema (HAE) is a rare, but serious genetic condition involving swelling in various body parts including the hands, feet, face, intestinal wall and airways.

According to the leading experts in immunology, when part of the immune system is either absent or does not function properly, it can result in an immune deficiency disease. When the cause of this deficiency is hereditary or genetic, it is called a primary immunodeficiency disease (PIDD). Researchers have identified more than 150 different kinds of PIDD.

People of all ages can be affected by eosinophilic esophagitis, with symptoms that may vary by age range and individual differences. Those who suffer from eosinophilic esophagitis have a large number of eosinophils—a type of white blood cell that is normally found in small numbers in the blood—and inflammation in the esophagus. A large number of eosinophils in the esophagus may result from a food allergy reaction, acid reflux, or airborne allergens, which can contribute to inflammation, or injury to the esophageal tissue.

People with drug allergies may experience symptoms regardless of whether their medicine comes in liquid, pill or injectable form. Symptoms can include skin rash or hives, itching, wheezing or breathing difficulty, swelling, or even anaphylaxis, a potentially life-threatening generalized systemic allergic reaction. Drug allergy reactions can occur in any part of the body.  Common drug allergies include Penicillin and related antibiotics, antibiotics containing sulfonamides (sulfa drugs), anticonvulsants, aspirin, ibuprofen and other nonsteroidal anti-inflammatory drugs (NSAIDs), and chemotherapy drugs.