Allergies occur when the body's immune system reacts to something it perceives as a threat. Usually, the substance is not harmful and most other people don't react to it. This exaggerated immune response can affect the skin, stomach and intestines or the respiratory system. It's not known exactly why people become allergic. What is known is that the body reacts only on a second or subsequent exposure to the allergen.
Skin Allergies
The exposure of the skin to chemicals can cause the skin to itch, swell or develop a rash (contact dermatitis). Substances such as latex, elastic, nickel and cosmetics are all common triggers of skin allergies. Eczema can also be due to an allergic reaction.
Food Allergies
The stomach and intestines are usually the site of symptoms from food allergies. Some of the most common foods that cause allergies are dairy products, eggs, strawberries, wheat, nuts, fish, shellfish and food dyes. Symptoms can include acid reflux, nausea, irritable bowel syndrome, diarrhea and vomiting. Other parts of the body can also be affected. People with food allergies can develop itchy or swollen lips and an itchy tongue or throat. They can also experience a runny nose, shortness of breath and difficulty swallowing. Fewer than 1 percent of Americans have true food allergies.
Food Intolerances
People with reactions to food are more likely to have a food intolerance than a food allergy. Food intolerances can cause similar symptoms to food allergies, especially acid reflux, nausea, irritable bowel syndrome and diarrhea. But they do not show up on allergy tests because the immune system response differs from that of an actual allergy.
Respiratory Allergies
The nose and lungs are usually the site of symptoms from respiratory allergies, also known as hay fever (allergic rhinitis) or asthma. Reactions such as sneezing, congestion, runny nose, itchy watery eyes and coughing occur when irritants are breathed into the body. Common irritants include grass pollens, tree pollens, mold spores, dust mites and animal dander. Fall is the worst time of year for people with these allergies because ragweed pollen is in the air. More than 36 million Americans are affected by seasonal hay fever.
Allergy Treatments
Physicians recommend avoiding allergy triggers. If that's not possible, drug treatment and immunotherapy are available. Drug treatment involves the use of antihistamines to relive symptoms. Decongestants and nasal sprays can also help lessen respiratory symptoms. Some of these drugs are available over the counter and others require a prescription.
Immunotherapy involves desensitizing the body against allergens by exposure to low doses of the allergen via shots or under the tongue (called sublingual therapy). The amount of the allergen is gradually increased over the course of two to three years of treatment. Immunotherapy is effective in about two-thirds of cases.
References
- UAB Medicine
- Medline Plus
- "Encyclopedia of Medicine;" The American Medical Association; 1989
