Causes

Allergies are usually inherited. But rather than allergies to specific allergens, what is inherited is the predisposition to be allergic. Therefore, children of parents who tend to be allergic are at a higher risk of being allergic themselves. Allergies could also develop as a result of being exposed to allergens when the immune system is weak, such as during convalescence or pregnancy.

Different kinds of allergies are caused by different kinds of allergens. The most common allergens are pollen and dust mites, both of which are airborne. Other airborne allergens include animal dander and mold. Latex and particular food substances also can cause allergic reactions.

Pollen can cause hay fever, medically known as allergic rhinitis. Hay fever results in inflammation and swelling of the lining of the nose, and in the protective tissue of the eyes. This causes reactions such as sneezing, itchy eyes, tears and congestion. Pollen is an allergen that can be very difficult to escape. A person with allergy can protect himself/herself against allergens such as food, medicines, and animal dander, by avoiding all contact with them. But because pollen is carried by the wind, it can find its way into different environments.

Dust mites are microscopic organisms that live in household dust, especially in furnishings. Household dust is a mixture of fibers from different fabrics, dander from animals, mold or fungus spores, food particles and other substances that could be potentially allergenic. If you look carefully at a shaft of sunlight, you can see particles of dust in it. Dust often contains dead dust mites and their waste. Dust mites live in warm, humid areas, thriving in summer and dying in winter. Dust mite allergy has symptoms similar to pollen allergy, and may also cause wheezing and coughing.

Molds are a kind of parasitic fungi that float in the air like pollen. They are too small to be seen by the naked eye. Usually, they are found in damp areas, such as shower stalls, damp basements, and refrigerator drip trays. Outdoors, they grow on rotting leaves and wood, in grass, hay, mulch, or under mushrooms. In rare cases, cheese processed with fungi can trigger allergic reaction. Like pollen, mold spores are airborne and particularly abundant in humid, warm weather. Symptoms of mold allergy include sneezing, congestion, itchy eyes, tears, runny nose, and coughing.

Animal dander is the scurf from the coat of an animal, such as a cat or a dog. It is not the fur itself that causes the allergy, as it is the proteins secreted by oil glands in the animal’s skin and the proteins present in an animal’s saliva, which stick to the fur when the animal licks itself. Urine is also a source of allergenic proteins. Allergies to animals can take two or more years to develop, and symptoms may not subside for as long as six months after contact with the animal has ceased. Carpet and furniture can be a source of animal dander and even after the animal has been removed, the air may carry the allergens. The symptoms are sneezing, congestion, and itchy, watery eyes.

Latex allergies are triggered by contact with rubber products. Rubber gloves are a very common source. Exposure to latex can be passive as may happen during a surgery. It can also be unknowing self-exposure, as when a latex-allergic person comes into contact with objects that may not apparently seem to be made of latex, such as garments with elastic, bottle stoppers, anesthetic face masks etc. Allergic reactions to latex can range from skin rashes and watery eyes, to much more serious symptoms.

Food allergies develop when the immune system is resistant to a particular food such as shellfish, peanuts, and tree nuts. In addition to these, milk, eggs, soy, and wheat are most known to cause food allergies in children. In response to the particular food, the body will then produce an IgE antibody that causes an allergic reaction within minutes of eating the food. Symptoms of food allergy include asthma (wheezing, coughing), hives, runny nose, vomiting, diarrhea, and swelling in the area around the mouth.

Insect venom, which usually enters the body through stinging, can cause a severe allergic reaction, which might require immediate medical attention. Typically, a sting might result in pain, swelling, and redness around the location of the sting. Sometimes, the swelling might extend beyond the location of the sting. For example, a person stung on the ankle may have swelling of the entire leg. But in the case of an allergic reaction, symptoms could include breathing trouble and wheezing; redness and skin rashes; swelling of the face, throat, or mouth tissue; rapid pulse; restlessness; and a sudden decrease in blood pressure.