The Basics Behind Allergic Reactions, Asthma and Pollen

Millions of people suffer from seasonal allergies while an ever-growing number of individuals fall victim to allergic symptoms resulting from exposure to pollen, Dust mites, dander, and everyday allergens. Symptoms can range from mild to severe, but the immune processes responsible for these reactions are the same in all cases.

A body's immune system is designed to fight off any foreign cell or object that it feels is harmful to the body. These foreign substances are commonly called antigens in relation to the immune system. Although antigens can be any kind of virus or bacteria, they can also be any number of allergens such as pollen, dust, or dander.

The body usually identifies allergens as harmful as soon as they enter the sinuses. The immune system responds by producing antibodies to fight off the allergen. Although the immune system produces antibodies in relatively small quantities the first time it encounters an allergen, subsequent exposures result in a greater immune response.

With repeated exposure, the body produces large amounts of the antibody specific to that allergen and stimulates cells in the respiratory system (nose, throat, eyes, and lungs – all called mast cells) to release histamine, a chemical responsible for traditional allergic symptoms such as a runny nose, coughing, itchy eyes, and sneezing. This same chemical is responsible for other allergic reactions in the skin that result in itches and some inflammation.

By releasing histamine and manufacturing allergic symptoms, the body has created a process to expel the allergen out of the body. Runny noses, coughing, and sneezing all help rid the body of the presumably harmful allergen.

Approximately 23% to 30% of the population in the US is genetically predisposed to pollen allergies. This means that their bodies automatically generate allergic responses to pollen, resulting in allergic symptoms. The remainder of the population does not have allergic reactions to either pollen or mold and can breath in these air particles without any obvious immune response.

Those who are predisposed to pollen allergies usually begin noticing symptoms in childhood. Those born to parents with allergies have a greater chance of becoming symptomatic during their lifetime. In fact, if one parent had allergies, the child has a 25% chance of inheriting those allergies. If both parents are symptomatic, the child has an estimated 75%-80% chance of becoming allergic.

Atopy, or the hereditary tendency to develop hypersensitive reactions to common antigens, is less common than hereditary allergies, but it still affects millions of individuals. Atopy immune responses generally manifest in parts of the body that are not in direct contact with the allergen and typically manifests as chronic asthmatic symptoms and reactions as a result of exposure to common allergens such as pollen. As many asthma sufferers know, seasonal variations in pollen and mold can trigger symptoms and asthma attacks.

Asthma

An estimated 20 million Americans have asthma, a chronic illness of the respiratory system that involves inflammation and constriction of airways as well as increased mucus production. Asthma is usually the result of hypersensitivity to certain triggers such as allergens, air temperatures, exercise or stress. Although scientists do not have a clear picture of the disease, doctors have been able to treat symptoms as they occur.

Individuals suffering from this disease usually experience breathlessness, tightness in the chest, and wheezing during symptomatic episodes and may cough periodically at night or in the early morning. All of these symptoms are the result of constricted airflow and respiratory inflammation and can be immediately reversed through treatment. Under some circumstances they can spontaneously reverse, but this is less common.

When specific, identifiable allergens trigger attacks and symptoms, these are called extrinsic asthma attacks. allergens like pollen can cause the body to release large amounts of histamine, exacerbating asthma by increasing mucus production in the lungs and creating inflammatory responses in the lung tissue. These histamines can also muscle contractions in the small branches of the lungs, causing wheezing and tightness in the chest. Furthermore, histamines have the capacity to increase the permeability of blood vessels, resulting in a decline of blood pressure and anaphylactic shock. This last reaction is rare, but can be fatal.

Asthma cases increased 75% between 1980 and 1994 and continue to grow. Millions visit emergency rooms annually for asthma related symptoms and asthma is responsible for an estimated 5,000 deaths a year. This disease is also the leading cause of student absenteeism.

Pollen

Pollen is blamed for many seasonal allergies as well as asthma triggers, but its purpose in nature is not to cause harm, but to reproduce. These tiny, microscopic particles are part of the plant's reproductive system and must be transferred to the appropriate parts of the flower in order to create viable seeds. Although some plants pollinate themselves, many rely on other means of transfer to carry their pollen to other plants for cross-pollination. In many cases animals, such as bees and other insects, carry pollen from one plant to another while they gather nectar for food. Other plants, however, rely on wind or water for cross-pollination.

Pollen that relies on wind for cross-pollination is the kind of pollen weather reports measure when they create pollen counts for the public. Typically this count represents the amount of pollen in a cubic meter or air measured over a period of 24 hours. Since pollen counts tend to be highest early in the morning on warm, dry days and lowest on cool, wet days, pollen counts tend to give more accurate representations of actual allergen counts when taken over the length of a day.

Plants with showy, colorful flowers usually rely on insects for pollination rather than wind and therefore don't usually appear on pollen counts. Wind-pollinated species such as oaks, ragweed, and grasses, spread pollen through air currents and are the types of pollen that produce allergic reactions in large numbers of individuals.

But different plants produce different kinds of pollen and some don't cause as much allergic reaction as others. The chemical makeup of pollen determines whether it will cause allergic symptoms and the physical shape of the pollen can determine reactions as well. The biggest culprits in the US are weeds such as ragweed, lamb's quarters, Russian thistle, English plantain, sagebrush, and redroot pigweed. Grasses also cause allergic reactions and the species that produce the most highly allergic pollen in North America include Kentucky bluegrass, Bermuda grass, Johnson grass, Timothy grass, sweet vernal grass, orchard grass, and redtop grass. Trees that produce the greatest allergens include ash, elm, oak, hickory, box elder, pecan, and mountain cedar.

Individuals suffering from seasonal pollen allergies constantly look for ways to alleviate their symptoms and remove the offending plants. Physical removal of plants, however, does little good since pollen can travel hundreds of miles on wind currents. Some of these plants, like ragweed, can produce a million grains of pollen in one day and can travel hundreds of miles from its origin.

Unfortunately for allergy sufferers, it only takes 20 ragweed pollen grains in a cubic meter of air to trigger an allergic reaction. Individuals suffering from pollen allergies should use personal room filtration systems that can effectively remove pollen from the air. Pollen measures about 10 to 60 micrometers in diameter and most indoor air purifiers with High Efficiency Particle Air (HEPA) filters can filter out air particles as small as 3 micrometers. Those affected by pollen should consider keeping their windows shut and using room or duct filters to condition their homes.

Although pollen is the most commonly known allergen, it is not the only cause of allergic reactions. According to a study from the Third National Health and Nutrition Study, a total of 54.3% of the tested population showed positive test results to allergens and 27.5% suffered from dust mite allergies. An additional 26.2% showed reactions to ragweed while another 26.1% tested positive for allergies to German cockroach feces. Other results in the study found that 18.1% of the population had allergies to Bermuda grass, 17% were allergic to cats, 13.2% to white oak and 86% to peanuts.