For most people, allergens themselves are not typically harmful; it's the allergy symptoms which are caused by the "false alarm" set off by their own immune systems that cause the discomfort and danger. The Centers for Disease Control and Prevention (CDC) estimates that up to 50 million American have or will develop sensitivity to some types of allergens. There seems to be a heritable link among the types of allergy sufferers; however, researchers are unsure of the underlying genetic mechanisms and how they may one day be used in stopping allergies before they start. Fortunately, the immune system's response to allergens is well understood, and many treatment options are available to help alleviate allergic reactions.
Foods
When your body incorrectly recognizes a food item as harmful, it triggers an immune response to fight off the allergen. According to the Mayo Clinic, your first exposure to a particular food allergen will often not illicit external allergic symptoms. You body will, however, produce antibodies specific to that food which circulate throughout your body long after the initial exposure. Upon your second exposure to the food allergen, the ever-alert antibodies recognize it right away and cause your immune system to release chemicals. The different ways these chemicals react to your body produce the many possible allergic symptoms you will experience, including runny nose, watery and itchy eyes, dry sore throat, hives, rashes, difficulty breathing, diarrhea, nausea and possibly anaphylactic shock. Common foods that act as allergens in some people include the proteins found in peanuts, walnuts, pecans, fish, eggs and shellfish. In children, milk is a common food allergen.
Pets
Any mammal can trigger human allergies, but most often they are associated with the commonest pets, such as dogs, cats, horses and rodents. Allergies result from human contact with animal proteins by direct touch or by hair and dander shed by the pet on furniture, floors or in the air. Pet allergies typically irritate the nasal lining causing a runny or stuffy nose and sneezing. In other cases, pet allergies can worsen asthma and cause the airways in the lungs to become inflamed and constricted. Asthma attacks induce wheezing and difficulty breathing and can become life-threatening if not treated.
Dust
Dust is made up of many potential allergens, including pollen, plant and animal fibers, mold and detergents. However, the primary causes of dust allergies results from exposure the fragments, feces and whole bodies of the microscopic dust mite. Dust mites are found everywhere in all homes. They feed solely on shed skin cells and thus are most abundant in bedding. Because they are found in sheets, pillowcases, mattresses and blankets, you end up putting your skin, mouth and nose in direct contact with these potential allergens each time you get into your bed. Dust allergies typically cause stuffy nose, watery eyes and sneezing. In some severe cases, they are responsible for the onset of asthma, which may require prescription medications to help open up the airways.
Other Common Allergy Causes
Human allergies have been reported for a wide variety of allergens. According to the National Institutes of Health (NIH), plant pollen is a significant and widespread allergen that occurs and worsens seasonally. Similarly, fungus spores, especially from mold, are allergens can cause an extreme allergic reaction. Stings and bites from insects and spiders, certain medications and even overexposure to sun can cause flareups in sensitive individuals.
